Choice of Major: The Changing (Unchanging) Gender Gap Author(s): Sarah E. Turner and William G. Bowen Source: Industrial and Labor Relations Review, Vol. 52, No. 2 (Jan., 1999), pp. 289-313 Published by: Cornell University, School of Industrial & Labor Relations Stable URL: http://www.jstor.org/stable/2525167 . Accessed: 04/03/2011 22:32 Your use of the JSTOR archive indicates your acceptance of JSTOR's Terms and Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp. JSTOR's Terms and Conditions of Use provides, in part, that unless you have obtained prior permission, you may not download an entire issue of a journal or multiple copies of articles, and you may use content in the JSTOR archive only for your personal, non-commercial use. Please contact the publisher regarding any further use of this work. Publisher contact information may be obtained at . http://www.jstor.org/action/showPublisher?publisherCode=cschool. . Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears on the screen or printed page of such transmission. JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. Cornell University, School of Industrial & Labor Relations is collaborating with JSTOR to digitize, preserve and extend access to Industrial and Labor Relations Review. http://www.jstor.org CHOICE OF MAJOR: THE CHANGING (UNCHANGING) GENDER GAP SARAH E. TURNER and WILLIAM G. BOWEN* Within the arts,sciences, and engineering fields, differencesbetween men and women in choice of college major have not lessened in the past two decades. In this paper, detailed data on choice of major and individual scores on the Scholastic Aptitude Test (SAT) are used to examine the extent to which observed differences between men and women reflect the effectsof pre-collegiate preparation (as reflected in SAT scores), as contrasted with a panoply of other forces. One conclusion is that there is a widening divide between the life sciences and math/physical science fields in their relative attractiveness to men and women. Differences in SAT scores account for only part of the observed gap, and an array of residual forces-including differences in preferences, labor market expectations, and gender-specific effects of the college experience-account for the main part of today's gender gaps in choice of academic major. D ifferences betweenmenandwomenin field of study chosen at the undergraduate level mayrepresentdifferencesin the skills that these groups bring to the labor marketand maypartiallyexplain observed differencesin wages. Choice of major, as well as decisions about where to attend college, is an importantlink in the chain of decisions and events that build human capital forthose fortunateenough *Sarah Turner is AssistantProfessorof Education and Economics at the Universityof Virginia and William Bowen is presidentof the AndrewW. Mellon Foundation. The authorsthankJohnBound, Charles Brown,Ronald Ehrenberg,Michael McPherson,Paula Stephan, Yu Xie, and Harriet Zuckerman forreading earlier draftsand providingthoughtfulcommentson this research. to go on to higher education. Choice of school, choice of major, and academic performance coalesce to influence options available to studentsforfurthereducation and career development. Choice of major is both an immediate outcome of the educational process and a determinantof later outcomes of many kinds. Understanding the factorsthatinfluence choice of major, for men and women, is one part of the larger process of understanding personal as well as societal returnsto varied investments in human capital. In addition to probing present-daypatternsin choice of major,we willinvestigate whether,and in what ways,these patterns have been changing. Have the choices of majors made by men and women converged? Or have traditional differences solidified or become even more pronounced in recent years? In(ldlstrial and LaborRelationsReview,Vol. 52, No. 2 (January1999). ? by Cornell University. 0019-7939/99/5202 $01.00 289 290 INDUSTRIAL AND LABOR RELATIONS REVIEW Among the manyfactorsthat influence men's and women's choice of major, and consequentlygender differencesin careers and wages, three factorsrelated to gender maybe particularlyimportant: a student's preparation and achievement at precollegiate levels of education, especiallyin mathematics; an individual's preferences forvarious courses of study,which maybe encouraged byparentaland societal expectations; and the labor market prospects associated witha given set of skills,which mayprovide more encouragement forone sex than the other to pursue certain fields of study. Our focus in this studyis on the firstof those factors-the extent to which differencesbetween men and women in precollegiate achievement (measured by SAT verbal and math scores) account for differencesin choice of major at the college level. Afterexamining the national trend in the choice of undergraduate major by men and women, we turnour attentionto thechoices made bymen and women at a small set of selectiveresearch universities and liberal artscolleges. National Trends and Descriptive Findings The Dissimilarity Index: Trends in National Data One startingpoint for measuring dissimilaritiesbetween women and men in choice of major is to calculate the absolute value of the differencesbetween the percentages of women and men majoring in each of the fields into which we classify students,sum these differences,and divide by two. This measure, referredto in other literatures (such as those on residential and occupational segregation) as an index of dissimilarity, captures the percentage of studentswho would need to change majors in order for parityto be achieved in the distributions,with 100% indicating complete segregationand 0% indicatingidentical distributions.1 'Jacobs ( 1995) appears to be the firstresearcherto have applied this measure to the differentdistribu- Movementsover the past 30 years in an all-inclusive dissimilarityindex and in a dissimilarity index limited to arts-sciencesengineering (A-S-E) are shownon Figure 1 forthe entirepopulation of B.A. recipients in the United States.2 The all-inclusive, "All-Fields"index is calculated using the numberofB.A. recipientsat all U.S. institutions in 10 broad field-of-study categories, including an array of professional fields that togetheraccounted forjust over half (53%) of all B.A. recipients in 1995. Just two fields-education and business-account fornearly2/3 of these B.A.s outside the arts-sciences-engineering fields. The "arts-sciences-engineering" (A-S-E) index is based on field choices made by studentswithin the arts-science-engineering disciplines (the remaining47% of B.A. recipients). The A-S-Eaggregate captures the range of concentrationsofferedat the undergraduate level at the institutionsincluded in thisanalysis. In the main, these selectiveliberal artsand research universities do not award degrees in professional preparatoryprograms such as business or education. Engineering programs,generally part of distinct engineering schools within the institution,represent the primaryundergraduate professional degrees offeredat theresearchuniversitiesincluded in this study;moreover,in manyinstances these programsof studycould as easily be called "applied science" as "engineering." tions of men and women byfield of study. The basic descriptive results presented here are substantively similarto his,withdifferencesattributableto the use of differentfield taxonomies. 2The 10 fieldcomposites used in the calculation of the "All Fields" dissimilarityindex are engineering, physicalsciences-math,lifesciences, psychology,economics, politics and other social sciences, scienceengineering technologies, humanities, education, business and communications,and a broadlydefined "other"categoryincluding the social servicesprofessions and vocational studies. The 7 field groups included in the "A-S-E"dissimilarityindex are engineering, physical sciences-math, life sciences, psychology, economics, politics and other social sciences, and the humanities. GENDER AND CHOICE OF MAJOR 291 Figure 1. Index of Dissimilarityamong B.A. Recipientsin theUnitedStates,1965-1994. 0.400.35- TotalDissimilarity Index 0.30 = 0.25 Education-Business- a 0 0.20 ~S 0.15 Arts-Sciences0.10 Engineering 0.05 I 0-00 65 IlI i1- 70 I I 75 80 I I I 85 90 95 Note:Basedon BA degreesconferred byU.S. collegesand universities reported in theHEGIS/IPEDS surveyscompiledin theCASPARdata archive."All BAs awarded"is used as thedenominator in the computation offieldsharesused to calculatethetotalindexofdissimilarity, as well as thecomponents attributable to thearts-sciences-engineering subsetoffieldsand theeducation-business-other subsetof fields. The All-Fieldsdissimilarity index showsa pronounced decline, froma high of nearly 40% in the 1965-66 academic yearto about 19% in 1994-95 (Figure 1). In aggregate, the largest decline in the overall index of dissimilaritytook place during the 1970s, with a drop of slightlymore than 10 percentage pointsoccurringbetween1973 and 1983. Focusing on the 1980s,Jacobs(1995) found verysimilar results for B.A. recipients,as well as advanced degree recipients. While that analysisalso suggested that the narrowingof the gender gap came to a halt in the mid-1980s, it did not distinguishthe role of the professionalfieldsfromthatof the arts and sciences in thisdynamic. The relationship between the piece of the dissimilarity index attributableto business-education-otherand thatattributable to arts-sciences-engineering changes over time, as a result of both changes in the degree of gender segregation within the component fieldsand the relativebalance between these two loosely defined subsectors of higher education. The dissimilarityindex declined until 1975 for both components. In business-educationit continued itsdownwardcourse after1975 (until 1985), but in arts-sciences-engineering it took an upward turn. Extremelylarge movements of women away from the field of education and the associated migrationof women into business programs account for much of the index. In the reduction in the dissimilarity mid-1960s, gender segregationoutside artssciences-engineeringaccounted fornearly two-thirdsof the total value of the dissimilarityindex. In this period, the undergraduate business major was more segre- 292 INDUSTRIAL AND LABOR RELATIONS REVIEW gated than some fieldswithinthe physical sciences, withwomen receivingonlyabout 10% of business degrees. By the mid1980s,women had entered undergraduate business programs in record numbers. Because of greatlyexpanded representation in business and greatlyreduced participation in the field of education, the portion of the dissimilarityindex attributable to fields outside the A-S-Ecomposite, primarilythese two fields, fell to a little more than 1/3. The movementsof the more restricted A-S-E index follow a verydifferenttrajectory,particularlyafter1975. This index of dissimilarityincreases through the early 1980s, before leveling off and declining moderatelyin the early 1990s. The "storyline"of thispaper is what did not happen to the dissimiliarity index within the arts-science-engineeringfields after 1975. During a period when other measures of economic outcomes and opportunitiesformen and women were conindex failed verging,theA-S-Edissimilarity to move towardgreaterparity.The remainder of thispaper uses new data thatinclude standardized testscores for individual students to explain more fullythan has been possible heretoforethe choices of majors bymen and women withinthe arts-scienceengineeringfields. ated (mostlyin the classes of 1955, 1980, and 1993). The advantage of these data for a micro-levelinquiryon choice of major is that we observe the full set of studentsat each of the twelveinstitutions.3 There are obviouslymanywaysin which areas of studycan be classifiedand aggregated. In keepingwithnormal practice,we have chosen to group all of the majors commonly considered to comprise the Humanities (including classics, English, foreignlanguages and literatures,history, philosophy, and religion); but we break withnormal practice in our decision not to group in single categories all of the Social Sciences or all of the Natural Sciences. Within the Social Sciences, there are pronounced gender-related differences between economics and psychology,and between each of these fields and the other social sciences. These patternsmayreflect, at least in part, differencesamong these fields in math-intensity.In the remainder of this paper, we workwith eight fields of study,some broader than others: the humanities; economics; psychology;politics and othersocial sciences; biologyand other lifesciences; mathematicsand physicalsciences; engineering;and a small number of students in "other" fields (principally architecture, communications, education, and speciallyconstructedmajors).4 The College and Beyond Database The data forthisinquiryare taken from theCollege and Beyonddatabase assembled by the Andrew W. Mellon Foundation in cooperation with34 colleges and universities. The part of the database used here consistsof detailed recordsof entrance test scores and majors subsequentlychosen by undergraduates at twelveacademically selectivecolleges and universities:threeuniversities (Princeton, Stanford,and Yale); six coeducational colleges (Hamilton, Kenyon,Oberlin, Wesleyan,Williams,and Swarthmore);and three women's colleges (Bryn Mawr, Smith, and Wellesley). The database includes all matriculantsin the 1951, 1976, and 1989 enteringcohorts,and we restrictour analysisto those who gradu- 3While we present some descriptive data for the 1951 enteringcohort,we restrictthe analyticalpartof this studyto the 1976 and 1989 cohorts. Although analysis of the choices of the 1951 cohort mightbe particularlyilluminating,the analysisis restrictedto the later twocohorts fortworeasons. First,standardized testing was far from universal in this period, leading to a large share of missingcases in thiscohort thatare unlikelyto be randomlydistributed.Second, the interpretationof shiftsin parametersbetween the 1951 cohort and later cohorts would be complicated bythe factthatseveral of these colleges and universities shifted from single-sex to coed status between 1951 and 1976. 4Whilethe humanitiespresentthe broadest aggregate of the fields listed, disaggregatingthis category does not add to the substance of the analysis. History and English are the largestsubfields,and the gender distributionsforthese fieldsare included in Table 1. A large numberof small fields,including philosophy, religion,specificforeignlanguages, and comparative GENDER AND CHOICE OF MAJOR 293 professionalfields. However, withinthe AThe large size and census-likecharacter of the database, itsrelatively"fine"level of S-E fields, the national distributionsfor aggregation,and the strongsimilaritiesin both men and women are surprisingly congruent with the distributions at our 12 admissionsstandardsand curriculaamong the 12 colleges and universitiespermit a schools (Appendix Table 1, top panel).5 This similaritysuggeststhat the forces incloser, more intensive, examination of male/female differencesin choice of mafluencing choice of major and the differences between men and women in making jors thanis possible in studiesusingsamples of individuals from a larger and more dithis choice extend well beyond this small verse arrayof institutions. To the extent set of selectiveprivateinstitutions. that choice of major is a decision made Distinguishingamong the 12 schools in thisanalysisbytyperevealspredictable diflargelyin a given institutionalcontext,it is ferencesin distributionsofmajorsbetween conceptually appealing to have data in the universitiesand the liberal artscolleges which we observe the full population of studentsat each oftheseinstitutions.Inter- (Appendix Table 1, bottom panel). With actions between choice of major and type significantnumbers of degrees conferred of institutionmaybias estimatesof returns in engineeringat the threeuniversities,the overall share of studentschoosing to major to specificfieldsofstudybygender and may in the humanities is notably lower at the confound the interpretationof aggregate researchuniversitiesthan at the liberal arts trendsin the choice of major formen and women. colleges, and this differenceis greaterfor The other side of the proverbialcoin is men than forwomen since more men major in engineering. The general patterns that these 12 institutionsare not at all representativeof American higher educaare consistentwiththe notion that the cotion. They represent a highly selective, educational liberal arts colleges and the entirelyprivate,subsetofinstitutionsoffer- women s colleges have similar"production functions,"with an emphasis on subjects ing what is generally regarded as a basic liberal artscurriculum.The threeuniversi- thatare more labor-intensivethan capitalties (and some of the colleges) do offer intensive,while the research universities undergraduate programs in engineering, offerundergraduates more opportunities in fields that require complex infrastrucand these schools also offera smallnumber of "other"majors. Still,the overwhelming tures and that attracthigh levels of sponsored research ("big science"). majority of all students in this database In most fields,the choices of majors by (roughly90%) majored in traditionalfields the women at the women's colleges can be withinthe humanities,the social sciences, said to be intermediatebetweenthechoices and the natural sciences. Unlike studies based on High Schooland Beyond,thisstudy made by women at the coeducational colis limitedbyan incomplete representation leges and the choices made by men at the of the population attending college from coed colleges. The share of women in the humanities is markedly lower in the anyhigh school cohort. From the perspective of national norms, the professional women's colleges than in the coed colleges fields (especially business and education) (41% versus 49%), while the shares of are grosslyunder-represented.We cannot, women in economics and in math-physical then, on the basis of these data, say anything about decisions to major in these literature,make up the remainderof the fieldsin the humanities. The largestchanges in gender compositionwithinthehumanitieshave occurred withinthese small and specialized fields. 5We compare our 1989 entering cohort with the 1993 B.A. recipients nationally because the largest. number ofour graduates earned theirdegrees in four years. There are some "s'ystemic" differences b)etwteen the "national" and "local" distributions,though tliesc differencesapply to both sexes. INDUSTRIAL 294 AND LABOR RELATIONS REVIEW Table 1. Changes over Time in Choice of Major, Graduates Only. (12 Institutions,Collegeand BeyondData) 1951 Cohort 1976 Cohort 1989 Cohort Field ofStudy W% M% Diff W% M% Diff W% M% Diff Humanities English History Other Humanities Economics Psychology Politics & 0th Soc Sci Tot Soc Sci Life Sciences Math/PhySci Tot Natural Sci 54.8% 14.9% 11.3% 39.7% 11.4% 13.2% 15.1% 3.6% -1.9% 43.1% 12.4% 6.8% 31.9% 8.1% 10.1% 11.2% 4.3% -3.3% 42.4% 12.5% 8.9% 33.6% 8.8% 10.6% 8.8% 3.6% -1.7% 28.6% 2.4% 5.2% 15.1% 10.1% 4.4% 13.4% -7.7% 0.8% 23.9% 7.5% 7.9% 13.6% 12.4% 5.2% 10.2% -4.9% 2.7% 21.0% 5.4% 9.0% 14.2% 9.9% 4.1% 6.8% -4.5% 4.9% 18.0% 25.7% 3.3% 4.5% 7.9% 11.9% 6.1% 26.4% -0.8% 6.4% -3.0% 10.9% -6.4% 17.3% -10.7% 15.8% 31.2% 11.7% 6.7% 18.4% 13.6% 31.1% 11.8% 9.7% 21.5% 2.2% 0.1% -0.1% -3.0% -3.1% 19.6% 34.0% 11.9% 5.7% 17.6% 18.9% 32.9% 9.5% 10.0% 19.5% 0.6% 1.1% 2.4% -4.3% -1.9% Engineering 0.3% 10.9% -10.7% Other/NEC 11.4% 5.7% 5.7% TOTAL 100.0% 100.0% Index of Dissimilarity:a Broad 21.5% Disaggregated 27.7% 2.7% 4.6% 100.0% 11.4% 4.1% 100.0% -8.7% 0.5% 3.6% 2.4% 100.0% 11.8% 2.2% 100.0% -8.2% 0.3% 11.8% 16.7% 10.1% 17.0% aThe broad index of dissimilaritytreatsthe social sciences and natural science subtotalsas single entries;the disaggregated index treatsthe components of these disciplines as individual fields (for example, for the social sciences, economics, psychologyand politics/othersocial sciences). science in the women's colleges are higher than the correspondingshares in the coed colleges. However, because selection bias maybe at work,judgmentsabout themeaning of thispatternshould be suspended, as the women who choose to attend the women's colleges maybe more inclined to major in scientificfieldsthan theirpeers at coeducational institutions. The Dissimilarity Index Again: Trends within the 12 Institutions The dissimilarity index providesa convenientwayto assess both thedegree towhich male-femaledifferencesin choice of major have narrowedover the past threedecades or so within these 12 institutionsand the sizes of the gender gaps thatremain. (For presentpurposes,we aggregatethedata for all 12 institutions;looking at subsets does not alter the main conclusions.) In brief, considerable convergence occurred be- tween 1951 and 1976: our disaggregated which treatseach of index of dissimilarity, the eight fields listed above as a separate field,fallsfrom27.7 for the 1951 entering cohort to 16.7 for the 1976 entering cohort. Driving this transformationwas the migration of women out of the humanities and into fields like economics and the life sciences, withthe share of women choosing economics risingfromless than 2.5% to 7.5% and the share choosing the life sciences growingfrom3.3% to 11.7% (Table 1). More surprising,perhaps, is the lack of furtherchange in the index between 1976 index is at 17.0 and 1989-the dissimilarity for the 1989 cohort. There were, however, interesting movements below this apparently placid surface. Within the sciences, gender differences at the field level widened in both the life sciences (where women moved into a position of over-representation) and math-physical GENDER AND CHOICE OF MAJOR sciences (where the over-representation of men increased). To the extent that men and women do not enter college with the same math and verbal skills,as measured bythe SAT, some differencesin patternsoffieldchoice would be expected. Replicatinga patternthathas been well established based on national data, theaveragemathSAT scoreforwomen at these 12 schools lags behind the average mathSAT score formen byabout 50 points in both the 1976 and 1989 cohorts;average verbal SAT scores forwomen and men were essentiallyequal in both the cohorts.6 Yet,the "gender gap" in math SATs does not translate into a proportionate difference in representationin each of the sciences, including the quantitativesocial sciences. To illustratethe need to consider the component fieldsof the sciences separately,Figure 2 shows the distributionof men and womenwithveryhighmathscores by field. In this bar chart, it is plain that women with high SAT scores are much more likelythan men to choose to major in the lifesciences and the humanitiesrather than engineering, math, or the physical sciences. If the paucityofwomen withvery high math achievement were the sole explanation fordifferencesin representation in the sciences and quantitativefields,then one would expect these distributionsto be identical for men and women. Relatively high mathSAT scores provide men withan advantage relativeto women in fields that require substantialquantitativeskills. Multivariateanalysis,based on testscores and choice of major byindividuals,providesan 6Atthe national level, the gap in SAT math scores between men and women was about the same as the gap withinthese institutions: the average SAT math score was 500 for men versus 454 for women (ETS data forcollege-bound seniors in 1989). The combination of highermathscores formen than forwomen and roughlyequal verbalscores means thatcombined SAT scores were higher for the men than for the women at our 12 schools (and nationally). There is some evidence that the "gender gap" in the mathematics SAT is narrowingin the 1990s, as the 1994 gap, nationwide,was 41 points,withaverage scores of 501 and 460 for men and women, respectively. 295 effectivemeans of describing howmuchof the gender gap is associated with differences in SAT scores. Other Studies and Approaches Differencesbetweenmen and women in choices of undergraduatemajor have been the subject of research by numerous sociand economistsover ologists,psychologists, the past several decades. In their 1997 surveyarticle,Leslie and Oaxaca identified over 120 theoreticaland empiricalanalyses of the under-representationofwomen and minoritiesin the science and engineering disciplines. Science policy analysts have often expressed the concern that the under-representationofwomen in thesedisciplines limitsthe pool of talententeringthe science and engineering work force. Beyond chartingaggregatesand flows,a number of researchershave attemptedto identifythe behavioral factorsexplaining why this choice process leads to such different observed outcomes formen and women. Theoretical explanations forthe differing outcomes tend to emphasize eitherdifferences in skills or differencesin preferences and environmental determinants. Men and women (or boys and girls) with the same measured skill sets may differ dramaticallyin theirpreferencesfordifferent typesofoccupations or courses ofstudy. Such differences may reflect biological forces or cultural factorssuch as the sexrole socialization forcescited byEccles and Hoffman(1984). Accordingto the sex-role socialization hypothesis,sex-role patterns and norms conveyed by schools and families in childhood affectlaterinvestmentsin education and training. Women may be encouraged to pursue fields and studies emphasizing nurturingwhile men are encouraged in domains emphasizing quantitative reasoning. While identificationof such sex-rolefactorsis inherentlydifficult, Corcoran and Courant (1985) suggested that variation in factorsaffectingsex-role socialization within gender groups (for example, variationin familystructure)provides one means ofdistinguishingthevariation in outcomes associated with sex-role INDUSTRIAL AND LABOR RELATIONS REVIEW 296 Than750 ofMenand WomenwithMathSAT ScoresGreater Figure 2. Distribution byChoiceofMajor. 30 Li Men 25 a A Women E c8OSHM20 0 ut . Huaiis c Eooic 15~~~~~~~~~~~Scecs i s h l0 scooy n Ohr oil BoLf Sine Mt hsc niern 20 norms from differencesin outcomes reflecting the presence of gender-specific barriersin employmentor wages. Expected labor force commitmentmay well affectthe economic rewards to any field of study, as suggested by Polachek (1978). Men and women maydifferin their intended labor forcecommitment,leading to markedlydifferentoptimal investments in human capital as captured bythe choice of major variable. For this reason, estimates ascribing gender differencesin occupational choice to employerdiscrimination may be overstated. As such, women withintermittent expected labor forceparticipation may favor fields with low "skill atrophy"or the lowest cost to labor force interruption, though available evidence suggests that this factor is not a primary empirical determinantof the observed differencesin choice of major Jacobs 1995). Experiences at the undergraduate level, including mentoringand peer influences, may have differentialeffectsfor men and women throughthe relative "costs" of any course of study. Several researchers, including Solnick (1995) and Baileyand Rask (1996), have focused on the role of the undergraduate institutionand the collegiate environment in determining the choice ofmajorbymen and women. Solnick (1995) presented an innovative study of how a student's desired field of study changes during college, and how the pattern of change varies by type of college attended. She found that women at allfemaleschools wereappreciablymore likely to switchto fields traditionallydominated bymen than were women at coeducational institutions.Since these resultswere based on transitionsduring college, Solnick argued that the cultural and academic environments associated with all-women's schools facilitatewomen's entryinto the sciences. The identificationofspecificeducational and instructionalfactorssuch as introductoryclass size and facultymentorshipdifferentially affectingchoice of majorbymen and women has received considerable at- GENDER AND CHOICE OF MAJOR 297 sorting men and women into particular fieldsof study. In particular,are the forces leading to differentchoices of major similar enough across fieldsthata model positing a dichotomous choice between science and non-science fields adequately characterizesobserved variation? Our answer to thisquestion is a clear "no." tentionbecause college administratorsare assumedto exercisesome controloverthese variables. Canes and Rosen (1995) investigated the extent to which increases in the share of female facultymembersin a given department-providing,in principle,more role models for female students-corresponded withgrowthin the representation offemalestudentsin thatdepartment.They found no evidence of such a link.7 While there is ample evidence that factorsother than achievementcontributeto the observed gender differencesin choice ofmajor at the undergraduatelevel,persistentdifferencesbetween men and women in high school courses and measured precollegiate achievementprovide at least a partial explanation for the gap. Skillbased explanations fordifferencesin field choices at the undergraduate level often focus on differences between men and women in measured mathematical skills and the number of high school courses completed in science and math.8A number of studies,including Ware and Lee (1988) and Ware, Steckler,and Leserman (1985), have included measures of achievement, particularlyin quantitative fields, as explanatoryvariablesin discretechoice models of the decision to major in a scientific field. However, such studies do not consider whether these measures varyin the magnitude of theireffectsacross the component fields of the sciences or across a more differentiatedset of fields. The observationthatwomen have demonstratedsizable gains in representationin some fields,notablythe lifesciences, while theirrelativeshareshave stagnatedin some quantitativesciences, leads to a reconsideration of the role of precollegiate skillsin In thispaper, our focus is on the extent to whichacademic achievement,measured by entering SAT scores, explains gender differencesin choice of major. While this parsimonious specificationof explanatory variables is plainlylimited,our data afford considerable power in explaining the behaviorof men and women across a range of fields of study. We quantifythe degree to which the observed gender differencesin choice of major can be attributed to precollegiateacademic achievement. Each individual'sSAT scoresare proxiesforskills brought to college, with the verbal and mathscoresrepresentingseparate (though oftencorrelated) typesof skills. Nevertheless, the most interestingbehavioral phenomenon is the piece thatremains unexplained. This residual element reflectssome combination of differentopportunities in the labor market for men and women and differencesin long-term occupational aspirations associated with gender. The multinomiallogitformulationiswell suited to the measurementoffactorsaffecting qualitative choices such as choice of major.9 In theory,choice of major foreach individual representsa deterministicout- 7Bailey and Rask (1996) tested the same hypothesis with micro data froma differentprivate liberal arts college and found modest support for the role model hypothesis. 8Since long-termexpectations maybe formedwell in advance of college enrollment,ascribing a causal interpretationto differencesassociated withachievement levels is unwarranted if these levels of precollegiate skill are endogenously related to long- term goals. For example, differencesin observed mathematicsachievement between men and women at the precollegiate level mayreflectdifferentiallevels of parental encouragement of sons and daughters in these courses at the secondary level. 9As discussed below, while the multinomial logit formulationoffersthe most tractableestimationof a qualitative choice problem, the functionalformalso leads to implicitassumptions associated withthe pa- AnalyticApproach and Estimation Strategy INDUSTRIAL AND LABOR RELATIONS REVIEW 298 come that maximizes utility. As researchers, we do not know enough about all the factorsaffectingthe choice-or their actual values-to replicate this calculation withouterror. Nonetheless, observations of individual achievement measures and choices of major provide sufficientinformation to make probabilistic statements. In particular,theprobabilitythatindividual i chooses field j over the alternative k is represented by (1) PmF= + Prob(VMF(Z, f3 ) e..> vM'F(Z., =Prob (e..- e.k> - + ek) 3M[) VMF(Z., fMF) MF)r), VMF(Z., where individual characteristicsin the vector Z. represent the observable determinantsoftheutilityfunction(V), theweights on these explanatoryfactorsare estimated as Pi,and the unknowncharacteristicsare captured in eY. In this framework,the gender-specificsuperscripts (M,F) recognize that men and women may differin theirunderlyingpreferencefunctionsand in the benefits(or costs) associated witha in a particularfield. particularcharacteristic Withan assumptionabout the distribution (Type I Extreme Value) of the residuals (ei ), we can estimatethe parametersof the model. In particular,if the epsilon terms are independentlyand identicallydistributed, the estimationprocedure followsthe multinomial logit formulation and the choice probabilitiestake the form VMF id .................... .........=................ ....... .... jE Jnexp M,F ~~~V id Answers to the interestingquestion of how we would expect individuals to sort themselvesamong fields, given their test rameter estimates. In particular, it is assumed that the residuals follow a well-behaved Type I extreme value distribution. A further(testable) restrictionis that the "independence of irrelevant alternatives" restrictionis maintained such thatthe elimination of one option (forexample, economics) does notchange the relative probabilities of the choices of other options (for example, humanities or math). scores, follow from the estimation of the coefficientsin this model. First, if the coefficientson math and verbal SATs are nonzero, then the model providessupport forthe hypothesisthatmore than one skill set mattersin the determinationof choice offieldand related investmentsin building human capital. Second, therelativemagnitude of the coefficientsindicates the degree towhichselection ofparticularmajors depends on mathand verbalproficiencyon entryto college. The objectiveofthisanalysisis to address the counterfactualquestion of how the distributionof the undergraduate majors of women would be expected to change if, holding preferencesconstant,women had the same distribution of SAT scores (X values) as men (Bound, Schoenbaum, and Waidman 1996).1o This typeof calculation allows us to estimate the effectson choice of major of differencesbetween men and women in both (a) theirprecollegiate academic preparation, measured here by the SAT scores that they bring with them to school, which are the X values, and (b) the waysin which women and men separately "convert"theirrespectiveSAT scores into choices of majors. These "residuals"are in turn the product of other forces and variables listed previously, including labor marketopportunitiesforwomen and men, wealth, other anticipated familycircumstances (which affectboth the desire for labor force participation and the need to earn sizable amounts of income), social and parental expectations, and attitudes and interestsstimulatedbyfacultyand fellow studentsin college. Empirically,thedifferencesbetweenmen and women in observed field distributions can be seen in the context of the familiar "0Thealternative is to considerhowthedistributionof majorsformen woulddifferif,giventheir of SAT preferences, theyhad the same distribution inthemagnitude ofthe scoresas women.Differences twocomponentpieces,dependingon whethermen the orwomenareusedas thereference group,reflect indexnumberproblemwiththistypeof underlying analysis. GENDER AND CHOICE OF MAJOR Oaxaca decomposition (2) pPFXF _ pPMXM + (PPFXM = (pFXF PpFXM) _PMXM) wherepMXM is the mean of the predicted probabilityof choosing field j using the coefficientsand values of the explanatory variablesformen;pPFXF is the mean of the predicted probabilityof choosing field j using the coefficientsand values of the explanatoryvariablesforwomen; and pPFXM is the mean of the predicted probabilityof choosing fieldj using the coefficientsfor women and values of the explanatoryvariables for men. The firstterm to the rightof the equal sign can be interpretedas the share of the observed differenceassociated withdifferences in SAT scores,while the second term shows the combined effectsof the differences associated with the coefficientsnot attributable to differences in measured achievement. In the case of a logit model or other nonlinear function, the magnitude of the effectof a change in any single exogenous factoris a functionof the level of the other variables used in this evaluation,and such nonlinear choice models do not allow for the decomposition of the effectsof particularexogenous variables. Empirical Results We begin by estimatingseparate multinomial logit models for men and women, with verbal and math SAT scores as the explanatoryvariables. Specifyingthe test score variables as categorical variables limits the functionalformassumptionswithin the logitframework(though italso permits some unconventional "hillsand valleys"in the implied distributionof majors by test scores). For the 1989 entering cohorts, estimated coefficientsand the associated standarderrorsare shownin Tables 2a and 2b." The significance of the parameter estimates(excepting thecase ofthe "other" "By aggregating across schools, we assume that individualsjointly select institutionand major. For 299 field group) supports the proposition that SAT scores help explain choice of major.12 For both men and women, high verbal scores in the presence of low quantitative scores have a strongand positiveeffecton the likelihood of majoring in the humanities (the reference group) relative to the probabilitiesof choosing all other majors. Stated the other way around, the nearly alongunbrokenrunofnegativecoefficients side the verbal SAT variables tells us that relativeto thegroup ofstudentswithverbal SAT scores below 550, ceteris paribus,studentswiththeserelativelyhighverbalscores are less likely to major in each of these fields than to major in the humanities. Relative magnitudes of the verbal coefficients also mediate choices among fields outside the humanities; for example, an increase in SAT verbal scores holding the example, since the liberal arts schools do not offer engineering programs, choosing to attend one of these institutionsis effectively choosing not to major in engineering. Aggregationalso disregardsthe question of whether the two-wayselection process-students choosing schools and schools choosing among applicants-affects the choice of major. Given these selection issues lurking near the surface, the coefficients should be interpretedas representingthe net effectof the institutionalselection process and the "true" test score effecton the choice of major. An alternative theoretical frameworkwould posit that institutionalchoice and choice of major are sequential. That type of analysis would be institution-specific. 12Asone early reader noted, it may be surprising that test scores seem to be such significantexplanatoryvariables determiningchoice of major and the differencesbetween men and women in choice of major. Two explanations meritconsideration. First, testscores are likelyto be correlated witha range of factors,including both other measures of academic achievement (such as high school rigoror high school' GPA) and socioeconomic variables. To this end, a causal interpretationof the parameter estimates as "explaining" differencesin choice of major is inappropriate,particularlyifthe magnitude of the correlation with omitted variables differsfor men and women. A second explanation, warrantingfurther investigation,is thatdifferencesin achievementmeasured by testscores are more powerfuldeterminants of choice of major in a constructwhere the achievementthresholdsforeach major are reasonablyhomogeneous frominstitutionto institution. 300 INDUSTRIAL AND LABOR RELATIONS REVIEW Table 2a. Multinomial Logit Estimatesof Choice of Major forWomen. (1989 Cohort, 12 Institutions) Math Scores ChoiceofMajor Humanities Economics Psychology ExplanatoryVariable Constant SAT> 750 SAT 700-750 SAT 650-700 SAT 600-650 SAT 550-600 Constant SAT> 750 SAT 700-750 SAT 650-700 SAT 600-650 SAT 550-600 Politicsa OtherSocial Sciences Constant SAT> 750 SAT 700-750 SAT 650-700 SAT 600-650 SAT 550-600 Sciences Biology-Life Constant SAT> 750 SAT 700-750 SAT 650-700 SAT 600-650 SAT 550-600 Math-PhysicalSciences Constant SAT> 750 SAT 700-750 SAT 650-700 SAT 600-650 SAT 550-600 Constant Engineering SAT> 750 SAT 700-750 SAT 650-700 SAT 600-650 SAT 550-600 OtherFields(NEC) Constant SAT> 750 SAT 700-750 SAT 650-700 SAT 600-650 SAT 550-600 No. Obs. X2(70) CoefficientStd.Error Reference Group -1.9159 (0.2107) 2.3380 (0.3770) 1.8124 (0.2746) 1.2625 (0.2552) 1.0963 (0.2544) -0.0250 (0.3055) -1.3916 (0.1588) 0.8581 (0.3442) 0.9206 (0.2074) 0.2793 (0.1980) 0.5001 (0.1891) 0.0976 (0.2005) -0.4786 (0.1149) 0.5440 (0.2452) 0.2106 (0.1571) 0.0147 (0.1409) 0.1523 (0.1379) -0.1180 (0.1436) -1.8376 (0.1873) 2.2891 (0.2809) 1.7375 (0.2201) 1.3758 (0.2085) 0.9013 (0.2169) 0.6547 (0.2230) -2.9104 (0.2996) 3.0099 (0.3805) 2.1529 (0.3327) 1.4245 (0.3281) 1.1945 (0.3335) 0.7917 (0.3495) -3.6820 (0.4312) 4.2719 (0.4923) 3.0523 (0.4576) 1.8321 (0.4617) 0.9739 (0.5004) 0.2542 (0.5645) -2.5102 (0.2728) 0.4750 (0.6720) 0.3794 (0.4095) 0.6545 (0.3413) 0.3272 (0.3560) 0.3922 (0.3458) 4290 533.14 Log Likelihood math score constant would increase the probabilityof majoring in biology relative to theprobabilityofmajoringin economics formen and women. Similarly,the higher VerbalScores Coefficient Std.Error -3.0289 -2.5770 -1.7221 -1.7222 -0.6350 (0.6122) (0.3191) (0.2192) (0.2400) (0.1934) -1.2115 -1.3127 -1.0657 -0.5789 -0.0057 (0.3433) (0-2331) (0.1924) (0.1808) (0.1655) -0.9104 -0.9321 -0.6279 -0.2932 -0.0617 (0.2518) (0.1689) (0.1398) (0.1352) (0.1315) -1.0460 -1.0620 -0.8131 -0.6795 -0.2224 (0.2766) (0.1949) (0.1689) (0.1730) (0.1658) -0.9453 -1.0464 -0.7585 -0.5320 -0.1984 (0.3641) (0.2707) (0.2363) (0.2400) (0.2363) -1.5511 -1.8584 -1.3056 -0.5633 -0.0514 (0.4618) (0.3676) (0.3096) (0.3009) (0.2949) -1.7445 -0.9632 -1.0056 -0.9063 -0.8437 (0.7548) (0.3588) (0.3129) (0.3152) (0.3194) -6,962.2844 the student's math SAT, the greater the probabilitythat the student will major in fields other than the humanities. But the magnitude of the effectof math SATs dif- GENDER AND CHOICE OF MAJOR 301 Table 2b. Multinomial Logit Estimatesof Choice of Major forMen. (1989 Cohort, 12 Institutions) Math Scores ChoiceofMajor ExplanatoryVariable Humanities Economics Constant SAT> 750 SAT 700-750 SAT 650-700 SAT 600-650 SAT 550-600 Psychology Constant SAT> 750 SAT 700-750 SAT 650-700 SAT 600-650 SAT 550-600 Politics& OtherSocial Sciences Constant SAT> 750 SAT 700-750 SAT 650-700 SAT 600-650 SAT 550-600 Sciences Constant Biology-Life SAT> 750 SAT 700-750 SAT 650-700 SAT 600-650 SAT 550-600 Constant Math-PhysicalSciences SAT> 750 SAT 700-750 SAT 650-700 SAT 600-650 SAT 550-600 Engineering Constant SAT> 750 SAT 700-750 SAT 650-700 SAT 600-650 SAT 550-600 OtherFields(NEC) Constant SAT> 750 SAT 700-750 SAT 650-700 SAT 600-650 SAT 550-600 CoefficientStd.Error Reference Group -1.3075 (0.3003) 1.9498 (0.3564) 1.2388 (0.3329) 0.9797 (0.3279) 0.5725 (0.3439) 0.2407 (0.3821) -1.6224 (0.3473) 0.5688 (0.4708) 0.1497 (0.4165) 0.2710 (0.3994) 0.3733 (0.4048) 0.4199 (0.4285) -0.1919 (0.1945) 0.2581 (0.2543) -0.0627 (0.2214) -0.1009 (0.2171) 0.0528 (0.2222) -0.2014 (0.2482) -1.5807 (0.3326) 2.1025 (0.3803) 1.2334 (0.3637) 0.7161 (0.3645) 0.2614 (0.3889) 0.3398 (0.4127) -2.0508 (0.4045) 3.1494 (0.4407) 1.7709 (0.4314) 0.9211 (0.4371) 0.0453 (0.4891) 0.3394 (0.5031) -2.5625 (0.5190) 4.0940 (0.5457) 2.6755 (0.5382) 1.7179 (0.5424) 1.1144 (0.5657) 1.0124 (0.5950) -2.5706 (0.5259) 1.3844 (0.6395) 0.6665 (0.6010) 0.6173 (0.5850) -0.2292 (0.6698) 0.5061 (0.6366) No. Obs. x2(70) 3,373 579.36 Log Likelihood VerbalScores Coefficient Std.Error -1.5184 -1.6997 -1.4903 -0.7848 -0.6173 (0.3553) (0.2456) (0.2186) (0.2035) (0.2070) -1.3777 -1.3382 -0.8578 -0.7690 -1.0075 (0.5648) (0.3534) (0.2832) (0.2827) (0.3111) -1.0043 -0.7779 -0.5172 -0.2087 -0.2095 (0.3070) (0.1969) (0.1735) (0.1702) (0.1735) -1.6352 -1.1582 -0.7252 -0.5337 -0.8396 (0.4119) (0.2496) (0.2223) (0.2242) (0.2493) -1.2464 -1.0619 -0.9664 -0.8358 -0.4635 (0.3534) (0.2527) (0.2401) (0.2489) (0.2502) -1.8427 -1.5820 -1.0985 -0.8272 -0.6815 (0.3586) (0.2400) (0.2178) (0.2218) (0.2317) -1.1917 -1.5164 -0.9247 -0.6124 -0.8416 (0.6796) (0.4897) (0.3973) (0.3868) (0.4283) -5,881.4223 fers appreciably across the fields."3 For both men and women, increases in the math SAT increase the probabilityof majoring in engineeringor math-physicalsci- 13More generally,testsof the hypothesisthatall of the coefficientsare equal to zero for each major and testsof the equality of coefficientsacross majors are rejected nearlyacross the board (there are 28 pairwise 302 INDUSTRIAL AND LABOR RELATIONS REVIEW ences relative to any other field, holding the verbal score constant. Note that in these fields,relativelylarge changes in the choice probabilities occur near the top of the scale. This result reinforcesthe intuitivelyplausible proposition that moving froma 700 to a 750 math score is likelyto have a much largerimpacton the probabilitythat a studentwill major in a field like theoretical physics than will a shiftfrom 600 to 650. Increases in mathSAT scores have a uniformlypositiveeffecton the probabilityof majoring in economics and the life sciences relative to the probabilityof majoring in the humanities,as indicated by the positive parameter estimates. However, changes in mathscores do not have as large an effecton the expected probabilities of choosing these fields as they do in the physical sciences and engineering. Little can be said about the variationin the probabilityof choosing to major in psychology associated with test scores, as the parameter estimatesare small in magnitude for women (thoughstatistically significant)and generally indistinguishablefrom zero for men. Calculating themarginalprobabilitiesthe predicted change in the probability associated with an incremental change in an explanatoryvariable-indicates therelative sensitivityof each field choice to changes in math and verbal scores. A key facet of the multinomialestimationis the tests for each gender group). At the 1% level of significance,the exceptions are psychology-political sciences (men and women), other-humanities (men and women), other-psychology(men and women), other-politics(men and women), other-biology(men and women), math-physical sciences-engineering (men only), economics-other (men only), psychology-politics (men only), and biology-math-physical sciences (women only). These tests suggest that relativelyhigh SAT scores (particularlyin the quantitativedimension) increase the probabilitiesof majoring in both the lifesciences and the physicalsciences forwomen, while formen there is greaterseparation between the life sciences and the physicalsciences in the upper dimensions of the SAT range. fact that the magnitude of the marginal effects-illustratedas the slope of a function relating the explanatory variable to the expected probabilityofmajoringin any given field-depends on the level of the individual's scores. Since the models use categoricalexplanatoryvariables,a discrete parallel is themeasurementoftheexpected change in the probabilityassociated witha movementbetween achievementscore categories. Figures 3 and 4 trace,forwomen and men, respectively,the expected probabilities associated with each field choice and combination of math and verbal achievement categories. A flathorizontal plane would be indicativeofa fieldin which the choice probabilities did not varywith test scores, while a plane with a constant slope would indicate a field in which the choice probabilityincreased or decreased steadilywithachievementscores. The "shapes" of the predicted functions are, withsome exceptions,quite congruent for men and women, though the levels of the planes differ. In the case of the humanities, the surface moves up from the low verbal, high math corner to its maximum in the high verbal, low math corner. As expected, the probabilityof majoringin engineering and math-physical science rises at an increasing rate withhigh math SAT scores. For both men and women, the highestprobabilityofchoosingmath-physical sciences is associated withtop category mathand verbal scores,while the probabilityof choosing engineeringbears less relation to the verbal score. Comparing the picturesformen and women, note thatthe rise in probabilitiesassociated withmoving from the penultimate to the highest categoryin math SATs is noticeablylargerfor men than forwomen. The predicted probability of majoring in engineering for women withmodest math scores (between 600 and 650) is close to zero (the picture resemblesa throw-rug) ,whilethepredicted probabilityformenwithscoresin thisrange is decidedly higher. The graphs for economics and the life sciences suggest a topographywith more hills and valleysand somewhatgreaterdifferencesby gender than are found for the GENDER AND CHOICE OF MAJOR otherfields. For men, twogroups are most likelyto major in economics: those with moderatelyhigh SAT scores (650 to 750) and low verbal scores and those withboth high verbal and high quantitative scores. For women, those withthe highestquantitativescores (greater than 750) and lowest verbal scores (less than 550) are mostlikely to choose to major in economics, while those withhigh scores on both dimensions of the SAT are less likelyto choose economics than those with low scores on both dimensions. In the life sciences, the choice probabilities for men rise modestly with math and verbal testscore categories until theyreach a "hilltop"withverbal scores in the 650 to 700 range. For women,theplane continues to slope modestlyupwardas both math and verbal scores rise, reaching its peak in the categoryreflectingthe highest combined scores. These figures provide fascinatinginsightsinto the sometimesdifferentwaysin whichwomen and men "convert"mathand verbalaptitudesintochoices of majors. We now employthe decomposition strategy outlined in the previous section in order to evaluatetheimportanceofSAT scores in explainingdifferencesin the majorschosen bymen and women. The resultsforthe 1989 cohort,usingwomen as the reference group, are presentedin Table 3. The table shows three sets of differences: the total observed differencesin the actual distributions;14 the differencesattributableto differencesbetween women and men in SAT scores (or "attributes"or X values); and the remaining differences,attributableto differences in "preferences" and other unspecified variables. These differencesare computed fromthe observed distributions of men and women and the distribution predicted using the SAT scores observed for men and the estimatedparametersfor women. (We made analogous calculations '4From the firstorder conditions of the log likelihood function,it can be shown that the mean of the predicted values is equal to the population shares. 303 Table 3. Decomposition Analysis of Model of Undergraduate Choice of Major: College Graduates Only, 1989 Cohort, Nonlinear Model. Field (A) (B) 8.6% -4.5% 5.0% 5.1% -0.7% 0.4% 3.6% -3.8% 4.6% 0.8% 1.8% -1.0% (C) Unexplained Difference bySAT Observed Due to Scores SAT Scores [Exp %M Difference, % W- [Actual %W -Actual %M -Exp %M] %M] Humanities Economics Psychology Politics & Other Social Sciences Biology-Life Sciences Math-Physical Sciences Engineering Other 2.4% -2.2% 4.6% -4.3% -8.4% 0.3% -2.0% -2.7% 0.3% -2.3% -5.7% 0.0% Index of Dissimilarity 17.2% 7.5% 12.8% Notes: Calculations are based on a multinomial specificationthatincludes SAT Verbal and SAT Math scores as categorical variables. The 12 institutions include Stanford,Yale, Princeton, Kenyon, Oberlin, Swarthmore, Hamilton, Williams, Wesleyan, Bryn Mawr, Smith, and Wellesley. Column (A) presents the actual differencebetween the share of women majoring in a field and the share of men majoring in the field; column (B) is the differencebetween the actual share of women in a field and the predicted share of men, using the coefficientsfromthe multinomial estimation for women (Table 2a) and the actual SAT scores of the men at the 12 universities; and column (C) is,the differencebetween the predicted distributionof men and the observed distribution for men. using the SAT scores observed forwomen and the estimatedparametersformen; the resultsare not qualitativelydifferent.) In the case of the humanities,we find thatwhile the observeddifferencebetween the actual distributionsforthe women and men was about 8.6 percentage points (42% of the women majoring in the humanities, versus 34% of the men), about 5 percentage points of thisgap can be attributedto SAT scores; the remaining3.6 points indi- 304 INDUSTRIAL AND LABOR RELATIONS REVIEW Figure3. PredictedChoice of Major: ProfilesforWomen,1989 Cohort. 0275 /' ....0.25 Humanities 77 Biology- LifeSciences VERBAL 725 0.10 0.15 Econoicis 010- 0.05~ - _2 575 Sciences Biolog Phyical 0,25 ~~~~~~~~~~~~~~~~0.05 0.05 0-w 725AL~ syhoog 0.10 cate the degree to which women with the same math and verbal SATs as the men are more likelythan the men to major in the humanities. Similarly,the much greater tendencyformen thanforwomen to major in math-physicalsciences and in engineering also appears to be thejoint product of variationsin SAT scores (highermathscores for the men) and the relativelystronger preferences among men for these fields, though the relative magnitudes of these Egieein Eninern effectsare not at all equal. Test score differencesaccount for about 45% of the total gender gap in the math-physicalsciences fieldsand forabout 32% in engineering. In economics and psychology,differences between women and men in SAT scores explain onlya verysmall part of the gender gap-about 16% in economics and less than 8% in psychology. Instead, it is pronounced differencesin "preferences" and otherresidual forcesthatgenerate the GENDER AND CHOICE OF MAJOR 305 Figure 4. Predicted forMen,1989Cohort. ChoiceofMajor:Profiles *00S X.5 :0:.25 Humanities Humanities Economics Pyh725 o yAL large gender differencesin representation in these fields. In biology-lifesciences, the twoforcespull in opposite directions. Differencesin SAT scores alone would lead us to expect more men than women to major in these fields; however,women's preferences for the life sciences relativeto other fieldsare so much strongerthan men's that the net effectis that women are modestly over-represented. In summary,we find that differencesin 0.20 525 Biology- LifeSciences cience Math - Physical Sciences Biolgyifeer e725 E VERBAL SAT scores account forless than halfof the total gender gap. If men had the same preferencesas women but differedonly in the distributionof SAT scores,the index of dissimilaritywould drop to 7.5. As noted above, the qualitativeconclusions reached are much the same whetherwe use women or men as thereferencegroup. It should be emphasized that the share of the differential associated with test scores is appreciablylowerusing thistaxonomythanitwould INDUSTRIAL AND LABOR RELATIONS REVIEW 306 Table 4. Decomposition Analysis of Model of Undergraduate Choice of Major: College Graduates Only, 1976 Cohort, Nonlinear Model. (A) Field (C) Unexplained Difference bySAT Scores Observed Due to SAT Scores [Exp %M Difference, %W- [Actual %W -Actual %M %M] -Exp %M] Humanities 11.8% -4.9% Economics 2.7% Psychology Government& Other Social Sciences 2.0% Biology-Life Sciences -0.2% Math-Physical Sciences -2.8% Engineering -8.9% Other 0.3% Index of Dissimilarity 16.8% (B) 5.2% -1.0% 1.0% 6.5% -4.0% 1.8% 2.3% -0.3% -2.2% 2.0% -2.9% -2.6% 0.2% 0.1% -6.2% 0.1% 8.7% 10.5% Notes: See explanation in notes to Table 3 and estimationresultsin Appendix Tables 2a and 2b. be ifwe used a simple dichotomybetween science and non-science fields.'5 The same cross-sectionalanalysisapplied to data forthe 1976 enteringcohort yields generally-but not exactly-similar results (Table 4). (Logit estimatesappear in Appendix Tables 2a and 2b.) For these individuals,differencesin SAT scores explain a slightlyhigher fractionof the gender gap, particularlyin the physicalsciences, where the observed differenceis more than accounted forbydifferencesin testscores. In Table 5, we summarize the changes over thisintervalby comparing the decompositions for the 1976 and 1989 entering co- horts; changes in the overall size of the gender gap foreach field are apportioned between a component attributable to changes in the relativedistributionsof SAT scores for men and forwomen and a component attributable to shifts in preferences.'6 In general, changes in thedistribution of testscores formen and women had verylittleeffecton gender gaps. Changes in the preferences or forces other than measured achievement were the driving force in wideninggaps in psychology,the life sciences, and math-physicalsciences. For example, while the gap between the shareofwomenand theshareofmen choosing to major in biology-life sciences increased from a small over-representation of ofmen in 1976 to an over-representation women by nearly 2.5 percentage points, almost none of this change is attributable to changes in the SAT scores for men and women. In understandingthese transformations, a key piece of the puzzle is to distinguish the changing "weights"used by men and womenin matchingachievementlevelswith fieldsof studyfromchanges in overall levels of demand. For example, one might consider changes in the discipline of economics requiring greater levels of mathematics achievementas leading to changes over time thatare independent of gender, '6Combining the period-specific decomposition expressions, we obtain a measure of the extent to which the change in the gap between cohorts is related to changes in SAT scores or to changes in preferencesand other residual factors. In each field j at time t, G (pRFtXFt I =p=F XF _ pPFtXMt) + i pPMtXMt= (p5RXMt I _.p5MtXMt) I The change in the gap can be writtenas C -G. + '5The dichotomous distinction between non-science and science majors yields a total differenceof 10.26 percentage points, with 6.7 percentage points attributableto differencesin testscores and about 3.5 percentage points attributableto differencesin the residual. - [(p = [ (pI5FXFI F1XM_ pIFIXMt) pPMtXMt) - (p (pI3F -XFtJ pF3Ft _Ft-)XMt-_ p ,XM1 ,)] Mt-IXMt-))] j I I The firsttermto the rightof the equal sign represents the portion of the change due to changes in the respectivedistributionsof SAT scores, while the second termin square bracketscaptures the portion of the change attributableto changes in the difference in the relative magnitude of the beta coefficients. GENDER AND CHOICE OF MAJOR 307 Table 5. Decomposition of the Change in the Gender Gap in Field Preferences: 1976 to 1989 Entering Cohorts, 12 Institutions,College and Beyond Data. Field ofStudy Humanities Economics Psychology Politics & Other Social Sciences Biology-Life Sciences Math-Physical Sciences Engineering Other Level of Gap in 1976 0.1176 -0.0493 0.0273 0.0197 -0.0017 -0.0278 -0.0888 0.0031 Sign of Gapfor 1976 Direction ofChange, 1976-89 Total Change in Gap W>M W<M W>M W>M W<M W<M W<M W>M Narrow Narrow Widen Narrow Ch Sign Widen Narrow Narrow -0.0313 0.0044 0.0228 -0.0114 0.0262 -0.0154 0.0050 -0.0002 Changein Gap Due to Changein SA7'Scores -0.0017 0.0022 -0.0056 -0.0046 0.0004 0.0095 -0.0005 0.0003 Changein Gap Unexplained byChange in SAT Scores -0.0296 0.0022 0.0284 -0.0068 0.0258 -0.0248 0.0055 -0.0006 Note: Components of change are calculated fromTables 3 and 4. See textfor details of calculation. while factors such as the opening of the medical profession to women would be likelyto have particularlystrongeffectson women's choices. A confounding force is the change in the overall demand for particular fields of study,which can serve to expand or contractthemeasured gaps without affectingthe relativerepresentationof men and women by field. Because data on SAT scores for the year 1951 are widelyavailable foronlyone ofthe schools examined in our study,we will not burden the text of the paper with regressions,tables,or figuresbased on thosedata. The admittedlyincomplete evidence suggests,however,thatlarge-scaleshiftsin preferences (especiallybywomen) were mainly responsible for the pronounced shrinking of gender gaps in choice of major between the mid-1950s and the late 1970s. In the 1951 enteringcohort,womenwiththesame SATs as men made radically different choices of majors; however,by the time of the 1976 cohort,preferenceshad converged to a considerable extent. We interpretthis resultas a reflectionof theopening up over thisperiod ofmanymorejob opportunities forwomen in traditionallymale fields,the greatercommitmentofwomen to extended labor force participation, and a general "loosening"ofstereotypesas towhatwomen and men should do withtheirlives. There were dramatic contractionsin the sizes of the preferencecomponents of the gender gaps in all of the predominantly male fields-and also in the humanities. It is against this background that we should interpretwhat did nothappen between the times of the 1976 and 1989 cohorts. As we saw in Table 5, the sizes of the preferencecomponentsof thegender gaps not only failed to continue to shrink,they rose in psychologyand the life sciences (withwomen expressingeverstrongerpositive preferences), and theyrose in math/ physicalsciences too (withwomen expressing much less interestthan men, as compared withthe situationin 1976). In short, the social and economic forcesthatpushed fora convergence in choices of major after the mid-1950s either spent themselvesby the late 1970s or were subsequently overtaken bynew forces. More recently,differences between men and women in choice of major appear to have become entrenched, in spite of modest continuing convergencein SAT scores;gender-specific preferencesnow appear to be widening a number of gaps rather than narrowing them. Conclusion and Open Questions The decompositions of gender gaps re- 308 INDUSTRIAL AND LABOR RELATIONS REVIEW ported in thispaper are entirelyconsistent with the commonly held view that differences in the academic preparation of women and men help explain observed differences in characteristic choices of major. The more strikingconclusion is thatdifferencesin SAT scores are nothing like the full story. In fact, they capture much less of the dynamicsof change over the past 35 or 40 yearsthan do the panoply of residual forces,including differencesin preferences, labor market expectations, gender-specificeffectsof the college experience, and unmeasured aspects of academic preparation. To answerdirectlyone of the questions posed at the startof the paper, we do notsee continuingmovement toward gender neutralityin the skills (or credentials) that students take from college. One possible interpretation is that women and men typicallyattach different "weights"(or values) to the after-college opportunitiesassociated witheach area of study.Recognizingpotentialfamilyresponsibilities,women maypreferfieldsin which skills are unlikely to atrophy or become obsolete-for example, formembersof the 1976 cohort, a keen understanding of Shakespeare mayprovide more opportunities in the 1990s than knowledge of the (nearly obsolete) COBOL computer language. Yet, this "depreciation effect"may be more importantin theorythan in practice. As women are observationallyless and less likely to interrupt their labor force participationforprolonged periods oftime to raise children, one would expect the gender gap in field choice to narrow accordingly-and it has not. A second typeofexplanation is thatthere continue to be impediments in the labor marketto women receivingthe same wages and professional opportunities as men in occupations related to particular majors. To some extent,measures of wage premia associated with undergraduate major are indicative of observed market incentives (or disincentives) to pursue certain fields that may varyby gender. Following wage regression estimates from Brown and Corcoran (1997) that use data from the National LongitudinalSurveyof theClass of 1972, we see that women with a college degree receivea higherpremiumthanmen in the humanities,a lower returnin biology,a slightlylowerreturnin mathand the physical sciences, and a much greater returnin engineering. If women in the 1989 enteringcohort observed these returnsas "prices" before choosing majors, then the over-representationof women in the life sciences and their under-representation in both the physical sciences and engineering would have to be seen as very surprising. Nevertheless, if undergraduate field choice is an intermediate step in transitions to professional fields such as law or medicine and to advanced academic study, then examination of the "final"labor force opportunities in these fields may help to explain gender differencesat the undergraduate level. In thisregard,theconsiderable widening of opportunitiesforwomen in medicine over the past two decades is consistent with the high participation of women in the life sciences at the undergraduate level. Grasping the underlying relationshipswould require detailed study of the linksjoining field choice, occupation choice, labor force participation,and remuneration. Otherpossibleexplanationsforthehardy persistenceofgendergaps include thepresence of unmeasured differences in precollegiate preparation in math, and marked variations in the experiences of men and women during the college years. Some have suggested thatSAT scores do a poor job of measuring higher order math skills. Given the same SAT scores,men may exceed women in the full specificationof math skills on college entrance, perhaps because theytend to take more advanced math courses in high school than their female counterparts. If this hypothesisis true,we would expect to see a significant relationship between academic performance and gender in the upper ranges of math SAT scores in courses requiring a high degree ofquantitativeskill. However, the data do not provide enough information to address the counterfactualquestion GENDER AND CHOICE OF MAJOR 309 ofhowan individualwould have performed ket expectations,gender-specificeffectsof the college experience, and unmeasured academically if he or she had chosen a differentfield of study. Since observed aspects of academic preparation-account forthe main part of today'sgender gaps in undergraduate performancemeasured by choice of academic major. GPA is conditional on field choice and It seems abundantlyclear thatthe simple course selection,the observedrelationship science-non-science dichotomy, however between undergraduate GPA and SAT helpfulit once was, is no longer usefulas a scores will not provide an answer to the counterfactualquestion of how a student taxonomyif the objective is to understand field choices by women and men. Quite who did not major in a particular field plainly,there is a wideningdivide between would be expected to performin thatsubthe life sciences, on the one hand, and ject. The choices men and women have made math-physicalscience-engineering,on the in elective fields of study at the underother hand, in their attractiveness to women. The magnitudeand persistenceof graduate level have not steadilyconverged. Differences in academic preparation of the disproportionatelyheavy representation of men in economics, as well as in women and men measured crudelyby test scores explain some ofthe persistentdiffer- engineering, mathematics,and the physiences in characteristicchoices of major, cal sciences, pose the puzzling question of whetherwe are attemptingto account for whythese fieldsare so differentfromother changes over the past three decades or for fields also classified broadly as "science." the cross-sectionalgap forthe most recent Perhaps thefindingsreportedin thispaper cohort. But such differencesin SAT scores will stimulatenew, even more determined, are onlypartof the story,and a modest part effortsto unravel the forces at work-a at that.An arrayofresidual forces-includhard task in part because of the need to ing differencesin preferences,labor mar- workacross disciplinaryboundaries. INDUSTRIAL AND LABOR RELATIONS REVIEW 310 co t F W~~~~~~ - Sc 00 -A4 ~~~~~z b: b: bz U~~~~~~~~~~~~~~~n b~ - 06 C; o C; n .^ ~ i\? So o @ !, F~~~~ Co * b w,?I0 i-e, -0 @ @ ~~~~ @ o 00 -c 0 0 i} 00 00 t~k ~ C1 ~ , NOv g - , - 00 - ~~ z t !0 L cCO o t 6 - CQ o o C; A ,2,O i~~. , ?,0xOm ?-OOe4 Cci?Q0ZQ0 ?~~~~~ t in C) -~~~~~~~~~~~~~~~~~~~~C - CO t-C; eee ? 'D s 'r- n o = v We:; gg ,!,9 o t 006 -.Oc Y ) ,~~ .1ge I c O2is s :, ,> o Cos -i Ci cl 0e CO xs~~~S G?0,,toG ? - uS GAsN eg A g . @ ~~~~~~~~~~~n 6 X1 ., 1 Cu i, <2 g -0 o C'~~ r- cli i .w -t o~~~~~~~~~~( b - o6 0 00 ti4, n~~~~~~~~~~~~~~~~~~ cl ~ Q~~~~~064 C~~~~~~~~~~~~~~~~~~~~~C sb 0 t in @ ,o <;s 00 OY - g i O CIA r g b0?bW e O ~~~~n ~ ~00 ce2,r2, eo ^ GA t.,o 00 0 Co - zo6. bs ;, i O:. Y gg egg e ,c 0 X~~~~~~~~~~~0 v O - (= =S - .. , @ S J 00 0o C~~~~~~~~~~~~~~~~~~~~~~~~~~I (I, C;ttsto m Kn - bs or C; r -0 00 sz0 AOC O C Co V oo ro v: t o ~~~~~~~~~~~~~~~~00 .; g 0 r o co- r - 8 N a14 s 0 t U - GENDER AND CHOICE OF MAJOR 311 APPENDIX TABLE 2A MultinomialLogit Estimates of Choice of Major for Women, 1976 Cohort, 12 Institutions Math Scores ChoiceofMajor ExplanatoryVariable Humanities Economics Constant SAT> 750 SAT 700-750 SAT 650-700 SAT 600-650 SAT 550-600 Psychology Constant SAT> 750 SAT 700-750 SAT 650-700 SAT 600-650 SAT 550-600 Politics& OtherSocialSciences Constant SAT> 750 SAT 700-750 SAT 650-700 SAT 600-650 SAT 550-600 Biology-Life Sciences Constant SAT> 750 SAT 700-750 SAT 650-700 SAT 600-650 SAT 550-600 Math-PhysicalSciences Constant SAT> 750 SAT 700-750 SAT 650-700 SAT 600-650 SAT 550-600 Constant Engineering SAT> 750 SAT 700-750 SAT 650-700 SAT 600-650 SAT 550-600 OtherFields(NEC) Constant SAT> 750 SAT 700-750 SAT 650-700 SAT 600-650 SAT 550-600 No. Obs. X2(7O) CoefficientStd.Error VerbalScores Coefficient Std.Error Reference Group -1.8367 1.2917 1.4866 0.8805 0.9573 -0.0424 -1.3174 -1.4079 0.5437 0.3728 0.2681 0.0879 -0.6176 -0.1716 -0.1394 -0.0410 -0.0916 -0.1123 -1.7144 1.9805 1.6226 1.4808 1.0326 0.6048 -2.4343 2.4570 2.2397 1.7028 1.0233 -0.0593 -4.0769 4.5923 3.7628 2.7454 2.0844 0.5316 -2.0654 0.3228 0.3536 0.0399 0.2437 -0.0608 3,742 478.37 (0.1794) (0.4340) (0-2391) (0.2262) (0.2035) (0.2385) (0.1500) (1.0269) (0.2429) (0.2081) (0.1903) (0.1906) (0.1159) (0.3747) (0.1953) (0.1571) (0.1429) (0.1396) (0.1665) (0.3267) (0.2178) (0.1943) (0.1899) (0.1968) (0.2293) (0.3705) (0.2680) (0.2567) (0.2608) (0.3153) (0.5153) (0.6147) (0.5552) (0.5566) (0.5595) (0.6772) (0.2031) (0.5213) (0.3012) (0.2753) (0.2406) (0.2512) Log Likelihood -2.8186 -1.3174 -0.9264 -0.5192 -0.1946 (0.7388) (0.2647) (0.2158) (0.1983) (0.1991) -1.1709 -1.5920 -0.8491 -0.4385 -0.6276 (0.4048) (0.2916) (0.2035) (0.1806) (0.2011) -1.4110 -0.7291 -0.4015 -0.3424 -0.2054 (0.3753) (0.1893) (0.1544) (0.1468) (0.1517) -1.8184 -1.1520 -0.9220 -0.5109 -0.2273 (0.3854) (0.2114) (0.1822) (0.1692) (0.1717) -1.5753 -1.0976 -0.5663 -0.5675 -0.4093 (0.4247) (0.2646) (0.2237) (0.2270) (0.2380) -2.4713 -1.7830 -1.5429 -1.0884 -0.5073 (0.6571) (0.3821) (0.3401) (0.3312) (0.3236) -0.2329 -0.4738 -0.4006 -0.2791 -0.4484 (0.4144) (0.3013) (0.2621) (0.2477) (0.2750) -6,199.9045 INDUSTRIAL AND LABOR RELATIONS REVIEW 312 APPENDIX TABLE 2B MultinomialLogit Estimates of Choice of Major for Men, 1976 Cohort, 12 Institutions Math Scores ChoiceofMajor ExplanatoryVariable Humanities Economics OtherFields (NEC) VerbalScores Coefficient Std.Error Reference Group Constant SAT> 750 SAT 700-750 SAT 650-700 SAT 600-650 SAT 550-600 Psychology Constant SAT > 750 SAT 700-750 SAT 650-700 SAT 600-650 SAT 550-600 Politics& OtherSocialSciences Constant SAT> 750 SAT 700-750 SAT 650-700 SAT 600-650 SAT 550-600 Sciences Biology-Life Constant SAT> 750 SAT 700-750 SAT 650-700 SAT 600-650 SAT 550-600 Math-PhysicalSciences Constant SAT> 750 SAT 700-750 SAT 650-700 SAT 600-650 SAT 550-600 Engineering CoefficientStd.Error Constant SAT> 750 SAT 700-750 SAT 650-700 SAT 600-650 SAT 550-600 Constant SAT> 750 SAT 700-750 SAT 650-700 SAT 600-650 SAT 550-600 No. Obs. X2(70) -1.6252 3.1139 2.3100 1.8069 1.5430 0.9604 -1.0490 0.5327 0.7194 0.0205 0.0044 -0.3277 -0.6701 0.6775 0.2605 0.3058 0.0588 -0.0002 -1.3874 2.2703 1.4690 1.2270 0.8169 0.5879 -1.6939 2.7773 1.5763 1.1829 0.4728 0.2192 -3.2957 4.9888 4.0782 3.3489 2.3605 1.5908 -1.8945 1.3688 0.9792 0.7507 0.6043 0.4877 3328 597.74 (0.2438) (0.3088) (0.2847) (0.2850) (0.2814) (0.3077) (0.1958) (0.3929) (0.2820) (0.2979) (0.2793) (0.3171) (0.1596) (0.2511) (0.2092) (0.2020) (0.2013) (0-2160) (0.2115) (0.2818) (0.2562) (0.2535) (0.2553) (0.2744) (0.2421) (0.3055) (0.2896) (0.2906) (0.3062) (0.3373) (0.5100) (0.5425) (0.5300) (0.5311) (0.5413) (0.5815) (0.2718) (0.4122) (0.3562) (0.3532) (0.3447) (0.3641) Log Likelihood -2.6888 -1.9104 -1.4658 -1.3178 -0.8984 (0.4380) (0.2218) (0.1891) (0.1961) (0.1938) -3.2838 -1.7121 -1.5078 -0.9599 -1.0449 (1.0319) (0.3205) (0.2738) (0.2543) (0.2739) -1.3547 -0.5890 -0.7094 -0.3019 -0.0559 (0.3959) (0.2051) (0.1909) (0.1856) (0.1839) -1.4368 -1.4364 -0.9901 -0.6880 -0.4564 (0.3495) (0.2297) (0.1962) (0.1966) (0.1987) -1.1365 -1.2053 -0.9338 -0.6573 -0.6774 (0.3438) (0.2437) (0.2203) (0.2228) (0.2389) -2.5161 -2.0634 -1.7096 -0.7798 -0.6250 (0.4099) (0.2408) (0.2136) (0.2002) (0.2099) -1.3552 -1.1728 -1.1115 -1.0985 -0.9142 (0.5230) (0.3167) (0.2838) (0.3004) (0.3035) -6,052.4772 GENDER AND CHOICE OF MAJOR 313 REFERENCES Bailey, Elizabeth, and Kevin Rask. 1996. 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