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Explorations in Economic History xxx (2008) xxx–xxx
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Explorations in Economic History
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Geography, insolation, and vitamin D in nineteenth century US
African-American and white statures q
Scott Alan Carson *
School of Business, University of Texas, Permian Basin, 4901 East University, Odessa, TX 79762, USA
University of Munich, CESifo, Shackstrasse 4, 80539 Munich, Germany
a r t i c l e
i n f o
Article history:
Received 12 February 2008
Available online xxxx
Keywords:
Nineteenth century US black and white
statures
Insolation
Vitamin D
a b s t r a c t
Using a new source of nineteenth century US state prison records I contrast the biological
living conditions of comparable African-Americans and whites. Although blacks and whites
today in the US reach similar terminal statures, nineteenth century African-American statures were consistently shorter than those of whites. Greater insolation (vitamin D production) is shown to be associated with taller black and white statures and a considerable
share of the stature difference between US blacks and whites was attributable to insolation
and vitamin D production. Black statures increased during the antebellum period, while
white statures declined. Black and white statures both decreased after the Civil War. Farmers were taller than workers in other occupations, and an alternative explanation for stature variation by social class is considered.
Ó 2008 Elsevier Inc. All rights reserved.
1. Introduction
The use of height data to measure living standards is now a well-established method in economics (Fogel, 1994, p. 138).
The average stature of a population reflects the cumulative interaction between nutrition, disease exposure, work, and the
physical environment (Steckel, 1979, pp. 365–367; Tanner, 1962, pp. 1–27). By considering average versus individual stature,
genetic differences are mitigated, leaving only the influences of the economic and physical environments on stature. When
diets, health, and physical environments improve, average stature increases and decreases when diets become less nutritious, disease environments deteriorate, or the physical environment places more stress on the body. Therefore, stature provides considerable insights into understanding historical processes and augments other welfare measures.
This study focuses on nineteenth century African-Americans and whites. Using a new source of data—nineteenth century
United States prison records—I contrast the heights of comparable black and white males in the US throughout the nineteenth century and also add a new explanation for black and white stature differences by socioeconomic status.
Black and white statures have the ability to reach comparable average levels when brought to maturity under similar biological conditions (Eveleth and Tanner, 1976, Appendix. Tables 5, 29, and 44; Tanner, 1977, pp. 341–342; Margo and Steckel,
1982). However, comparison of nineteenth century black and white statures demonstrates that blacks were consistently
shorter than whites, but we are less certain of the source for this difference (Margo and Steckel, 1982; Sunder, 2004; Carson,
q
I appreciate comments from participants at the Western Social Science Association, and the Center for Economic Studies at the University of Munich.
Comments from John Komlos, Marco Sünder, Tom Maloney, Larry Wimmer, Nina Jablonski, Paul Hodges, and Thomas Poder were particularly helpful. I am
also grateful for comments from two anonymous referees. Owen Wallace-Servera, Sandy Triepke, Kellye Manning, Brandon Hayes, and Anita Voorhies
provided excellent research assistance. All errors are mine.
* Fax: +1 432 552 2174.
E-mail address: [email protected].
0014-4983/$ - see front matter Ó 2008 Elsevier Inc. All rights reserved.
doi:10.1016/j.eeh.2008.09.002
Please cite this article in press as: Carson, S.A., Geography, insolation, and vitamin D in nineteenth century US ..., Explor.
Econ. Hist. (2008), doi:10.1016/j.eeh.2008.09.002
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S.A. Carson / Explorations in Economic History xxx (2008) xxx–xxx
2008). Moreover, any explanation must account for a robust geographical finding: blacks were shorter than whites in both
the South and the North (Margo and Steckel, 1992, p. 516).
An unexplored source for this white stature advantage and why Southerners were taller than Northerners in general may
be related to an important interaction between biology and geography. Calcium and vitamin D are two chemical elements
required throughout life for healthy bone and teeth formation; however, their abundance are most critical during younger
ages (Wardlaw et al., 2004, pp. 394–396; Tortolani et al., 2002, p. 60). Calcium generally comes from dairy products, and
vitamin D is not dietary but is produced by the synthesis of cholesterol and sunlight in the epidermis’ stratum granulosum
(Holick, 2004, pp. 363–364; Nesby-O’Dell et al., 2002, p. 187; Loomis, 1967, p. 501; Norman, 1998, p. 1108; Holick, 2007).
This paper illustrates that up to 50% of the white–black stature differential is attributable to lower black vitamin D production than whites.
Vitamin D is vital in all vertebrates because it allows them to absorb more calcium from their diets and contributes to
stronger skeletal systems and stature growth (Jablonski, 2006, p. 62).1 In order of importance, the primary sources of vitamin
D in humans are the amount of time exposed to sunlight, skin pigmentation, and nativity (Holick et al., 1981, p. 590). Greater
direct sunlight (insolation) produces more vitamin D, and vitamin D is related to adult terminal stature (Xiong et al., 2005, pp.
228, 230–231; X-ZLiu et al., 2003; Ginsburg et al., 1998; Uitterlinden et al., 2004). However, after the circulatory system contains sufficient amounts of vitamin D and to avoid vitamin D toxicity, vitamin D production is restricted within the stratum
granulosum and residual vitamin D is broken down into inert matter (Holick et al., 1981, pp. 591–592; Jablonski, 2006, p.
62; Holick, 2001, p. 20; Holick, 2004, p. 363). This self-limiting vitamin D effect may account for some of the difference between
how black and white statures were associated with insolation, because at North American latitudes whites are closer than
blacks to the natural threshold where vitamin D production is curtailed. At the opposite extreme, insufficient vitamin D has
been linked to rickets, osteomalasia, auto-immune diseases, and certain cancers (Holick, 2001, p. 28; Garland et al., 2006, pp.
252–256; Grant, 2003, p. 372).
Vitamin D production also depends on melanin in the stratum corneum (Norman, 1998, p. 1108), and lighter colored
nineteenth century blacks were consistently taller than darker pigmented blacks (Tanner, 1962, pp. 150–151; Tanner,
1977; Steckel, 1979, pp. 374–376; Margo and Steckel, 1982, pp. 532–534, Table 6; Bodenhorn, 1999, 2002; Xiong et al.,
2005, pp. 228, 231; Z Liu, 2003, p. 825). Greater melanin (skin pigmentation) in the stratum corneum interferes with vitamin
D’s synthesis in the stratum granulosum, and darker pigmentation filters between 50% and 95% of the sunlight that reaches
the stratum granulosum (Jablonski, 2006, pp. 80–81; Kaidbey et al., 1979, pp. 249 and 253; Loomis, 1967, p. 502; Weisberg
et al., 2004, p. 1703S; Holick, 2007, p. 270).2 Moreover, a common explanation for taller mulatto statures is that nineteenth
century social and economic forces favored fairer complexions over lighter complexions, and lighter colored blacks benefited
from these social and economic institutions (Margo and Steckel, 1982, p. 521; Bodenhorn, 1999, p. 983). Nonetheless, a more
complete explanation that addresses the interaction between stature, sunlight, and vitamin D production may be related to human biology.
It is against this backdrop that this paper addresses two paths of inquiry into nineteenth century African-American and
white stature variation. First, how did male statures vary with insolation across the US by nativity and race? This study illustrates that black and white statures were positively related to insolation, and black stature increases in insolation were
greater than white stature increases over the same insolation interval. Moreover, given that whites produce more vitamin
D with the same insolation and because vitamin D production is restricted when sufficient vitamin D is present in the circulatory system, the white stature rate of increase with insolation should have diminished before the black stature rate of
increase (Holick, 2001, p. 20). Second, after controlling for both nativity and the physical environment, how were statures
related to socioeconomic status? A new explanation that addresses the nexus between socioeconomic status, nutrition,
and exposure to sunlight is considered. Workers who spent more time outdoors exposed to sunlight were consistently taller
than workers who traditionally spent more time indoors, away from the stature benefits of solar radiation.
2. Nineteenth century US prison data
2.1. Prison records
The data used here to study black and white statures are part of a large nineteenth century prison sample. All state prison
repositories were contacted and available records were acquired and entered into a master data set. These prison records
include Arizona, California, Colorado, Idaho, Illinois, Kansas, Kentucky, Missouri, New Mexico, Ohio, Oregon, Pennsylvania,
Texas, and Washington (Table 1). Most blacks in the sample were imprisoned in the Deep South or Border States—Kentucky,
Missouri, Georgia, and Texas. Most whites in the sample were imprisoned in Missouri and Texas, but Northern whites were
also from Illinois, Ohio, and Pennsylvania. The Far West is also represented in the sample.
All historical height data have various biases, and prison and military records are the most common sources for historical
stature data. One common shortfall for military samples is a truncation bias imposed by minimum stature requirements
1
There are few dietary sources of vitamin D.
To address rickets in the US population, in the 1930s the federal government advocated fortification of the US milk supply with vitamin D (Bishai and
Nalubola, 2002, p. 41; Holick, 2004, p. 1679S). However, blacks, who are more likely to be lactase intolerant, did not consume milk to the same degree as that
comsumed by whites (Kiple and King, 1981).
2
Please cite this article in press as: Carson, S.A., Geography, insolation, and vitamin D in nineteenth century US ..., Explor.
Econ. Hist. (2008), doi:10.1016/j.eeh.2008.09.002
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S.A. Carson / Explorations in Economic History xxx (2008) xxx–xxx
Table 1
Nineteenth century US state penitentiaries.
Prison
Black youth
Arizona
California
Colorado
Georgia
Idaho
Illinois
Kansas
Kentucky
Missouri
New Mexico
Ohio
Oregon
Pennsylvania
Texas
Total
White youth
Black adult
White adult
N
Percent
N
Percent
N
Percent
N
Percent
21
71
113
317
6
250
232
1,480
2,003
27
734
11
521
5,400
11,186
.19
.63
1.01
2.83
.05
2.23
2.07
13.23
17.91
.24
6.56
.10
4.66
48.27
100.00
245
1,116
500
26
232
1,646
768
1,130
3,412
245
3,041
241
1,772
2,550
16,924
1.45
6.59
2.95
.15
1.37
9.73
4.54
6.68
20.16
1.45
17.97
1.42
10.47
15.07
100.00
177
362
808
998
98
971
745
4,763
8,476
317
4,545
50
3,378
21,956
47,644
.37
.76
1.70
2.09
.21
2.04
1.56
10.00
17.79
.67
9.54
.10
7.09
46.08
100.00
1,926
7,114
6,521
131
1,842
8,296
3,314
5,520
20,375
1,753
21,800
1,799
14,254
13,621
108,266
1.78
6.57
6.02
.12
1.70
7.66
3.06
5.10
18.82
1.62
20.14
1.66
13.17
12.58
100.00
Source: Data used to study black and white anthropometrics is a subset of a much larger nineteenth century prison sample. All available records from
American state repositories have been acquired and entered into a master file. These records include Arizona, California, Colorado, Idaho, Illinois, Kansas,
Kentucky, Missouri, New Mexico, Ohio, Oregon, Pennsylvania, Texas, Utah and Washington.
Notes: Stature is in centimeters. The occupation classification scheme is consistent with Ferrie (1997).
(Fogel et al., 1978, p. 85; Sokoloff and Villaflor, 1982, p. 457, Fig. 1; A’Hearn, 2004). Fortunately, prison records do not implicitly suffer from such a constraint and the subsequent truncation bias observed in military samples. However, prison records
are not above scrutiny. The prison data may have selected many of the materially poorest individuals who were drawn from
lower socioeconomic groups, that segment of society most vulnerable to economic change (Bogin, 1991, p. 288; Komlos and
Baten, 2004, p. 199; Nicholas and Steckel, 1991, p. 944). For height as an indicator of biological variation, this kind of selection is preferable to that which marks many military records—minimum height requirements for service (Fogel et al., 1978,
p. 85; Sokoloff and Villaflor, 1982, p. 457,Fig. 1). Moreover, if at the margins of subsistence demographic and socioeconomic
factors and insolation were more significant in stature attainment, prison records may illustrate these effects more clearly.
There also is concern over entry requirements, and physical descriptions were recorded by prison enumerators at the
time of incarceration as a means of identification which, therefore, reflect pre-incarceration conditions. Between 1830
and 1920, prison officials routinely recorded the dates inmates were received, age, complexion, nativity, stature, pre-incarceration occupation, and crime. All records with complete age, stature, occupation, and nativity were collected. There was
Density
0 .02 .04 .06 .08 .1
White Youth Stature
0
Density
.02 .04 .06 .08 .1
Black Youth Stature
88 90 92 94 96 98 100102104106108110112
88 90 92 94 96 98 100102104106108110112
Index
Index
White Adult Stature
.15
.1
Density
0
.05
.1
.05
0
Density
.15
Black Adult Stature
58 60 62 64 66 68 70 72 74 76 78
58 60 62 64 66 68 70 72 74 76 78
height
height
Fig. 1. National black and white stature histograms by age group (see Table 1).
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S.A. Carson / Explorations in Economic History xxx (2008) xxx–xxx
great care recording inmate statures because accurate measurement had legal implications for identification in the event
that inmates escaped and were later recaptured.3 Arrests and prosecutions across states may have resulted in various selection
biases that may affect the results of this analysis. However, black and white stature variation within US prisons is consistent
with other stature studies (Steckel, 1979; Margo and Steckel, 1982; Nicholas and Steckel, 1991, pp. 941–943; Komlos, 1992;
Komlos and Coclanis, 1997; Bodenhorn, 1999; Sunder, 2004). Because the purpose of this study is to compare nineteenth century male black and white statures, females and immigrants are excluded from the analysis.
Fortunately, inmate enumerators were quite thorough when recording inmate complexion and occupation. For example,
enumerators recorded inmates’ race in a complexion category, and African-Americans were recorded as black, light-black,
dark-black, and various shades of mulatto (Komlos and Coclanis, 1997). Enumerators recorded white complexions as light,
medium, dark, and fair. The white inmate complexion classification is further supported by European immigrant complexions, who were always of fair complexion and were also recorded as light, medium, and dark.4 While mulatto inmates possessed genetic traits from both European and African ancestry, they were treated as blacks in the nineteenth century US and
when comparing whites to blacks, mulattos are included with blacks.
Enumerators recorded a broad continuum of occupations and defined them narrowly, recording over 200 different occupations, which are classified here into four categories: merchants and high skilled workers are classified as white-collar
workers; light manufacturing, craft workers, and carpenters are classified as skilled workers; workers in the agricultural sector are classified as farmers; laborers and miners are classified as unskilled workers (Tanner, 1977, p. 346; Le Roy Ladurie,
1979; Margo and Steckel, 1992; p. 520). Unfortunately, inmate enumerators did not distinguish between farm and common
laborers. Since common laborers probably encountered less favorable biological conditions during childhood and adolescence, this potentially overestimates the biological benefits of being a common laborer and underestimates the advantages
of being a farm laborer.
Because the youth height distribution is itself a function of the age distribution, a youth height index is constructed that
standardizes for age to determine youth stature normality and whether there were arbitrary truncation points imposed on
inmate stature, either by law enforcement or state legislation. This index is calculated by first calculating the average stature
for each age group; each observation is then divided by the average stature for the relevant age group (Komlos, 1987, p. 899).
Fig. 1 demonstrates that black and white statures were distributed approximately normal and there is no evidence of age
heaping or arbitrary truncation points.
Table 2 presents black and white inmates’ age, birth decade, occupations, and nativity proportions. Although average statures are included, they are not reliable because of possible compositional effects, which are accounted for in the regression
models that follow. Whites were a larger portion of the prison population than blacks; 68.03% of this US prison sample was
white. Age percentages demonstrate that black inmates were incarcerated at younger ages, while whites were incarcerated
at older ages. Southern law evolved to favor plantation law, which generally allowed slave owners to recover slave labor on
plantations while slaves were punished (Komlos and Coclanis, 1997, p. 436; Wahl, 1996, 1997; Friedman, 1993). Blacks were
less likely to be incarcerated during the early nineteenth century; however, with passage of the thirteenth amendment, slave
owners no longer had claims on black labor, and free blacks who broke the law were turned over to state penal systems to
exact their social debt. Whites were more likely than blacks within nineteenth century US prisons to be white-collar, skilled
workers, and farmers and less likely to be unskilled.
2.2. United States’ insolation
To account for the relationship between vitamin D and stature, a measure is constructed that accounts for solar radiation.
Insolation is the incoming direct sunlight that reaches the earth, its atmosphere, and surface objects.5 Insolation is also the
primary source of vitamin D (Holick et al., 1981, p. 590; Holick, 2007, p. 270). Because of its distance from the equator, European
insolation is lower than African insolation, and before their migration to North America, Europeans had to be more efficient in
vitamin D production at low insolation latitudes. Before their forced migration to North America, Africans were exposed to considerable insolation, which was significantly greater than the insolation received by their progeny in the US. Because of its size,
Africa has a large insolation variation, and because of its proximity to the equator, its average insolation is greater than the insolation received in the US. For example, from a random sample of western African sites, West Africa receives approximately 5.6 h
of direct insolation per day with a standard deviation of .53 h; however, the US only receives 4.10 h of direct sunlight per day
with a standard deviation of .61 h and the difference is significant at acceptable levels.6
Because US historical insolation is unavailable, a modern insolation index (1993–2003) is constructed, and monthly insolation values are measured from January through June. The insolation index measures statewide average insolation levels
3
Many inmate statures were recorded at quarter, eighth, and even sixteenth increments.
I am currently collecting nineteenth century Irish prison records. Irish prison enumerators also used light, medium, dark, fresh and sallow to describe white
prisoners in Irish prisons from a traditionally white population. To date, no inmate in an Irish prison has been recorded with a complexion consistent with
African heritage.
5
Insolation is an acronym for incident solar radiation, and is a measure for sunlight energy received for a given surface area at a given time. If w equals watts,
m equals meters, and i equals insolation, i ¼ mw2 ¼ mkwh
2 day. Data for US insolation are available from the National Aeronautics and Space Administration at http://
eosweb.larc.nasa.gov/cgi-bin/sse/sse.cgi.
6
Western African sites include Ouagadougou, Burkina Faso; Yaoundé, Cameroon; Bangui, Central African Republic; Accra, Ghana; Gambia, Gambia; Conakry,
Guinea; Liberia; Nouakchott, Mauritania; Niamey, Nigeria; Freetown, Sierra Leone; Dakar, Senegal.
4
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S.A. Carson / Explorations in Economic History xxx (2008) xxx–xxx
Table 2
National prison data white and black descriptive statistics
White
Black
Mean difference
N
Percent
Mean
SD
N
Percent
Mean
SD
Ages
Teens
20s
30s
40s
50s
60s
70s
16,770
63,613
26,886
10,878
4,324
1,298
232
13.52
51.30
21.68
8.77
3.49
1.05
.19
169.74
171.94
171.98
171.89
171.62
171.26
170.95
6.70
6.51
6.48
6.51
6.52
6.71
6.43
11,171
31,625
10,196
3,759
1,333
448
92
19.06
53.95
17.39
6.41
2.27
.76
.16
167.98
171.10
171.29
170.73
170.35
169.80
169.03
7.45
6.88
6.72
6.81
6.99
6.48
5.91
1.76
.84
.69
1.16
1.27
1.46
1.92
Birth decade
1800s
1810s
1820s
1830s
1840s
1850s
1860s
1870s
1880s
1890s
1900s
906
2,467
4,200
7,988
16,506
24,982
25,194
22,044
12,741
6,567
406
.73
1.99
3.39
6.45
13.32
20.15
20.32
17.78
10.27
5.30
.33
172.41
172.52
172.44
171.79
171.46
171.30
171.68
171.63
171.68
171.90
170.67
6.50
6.56
6.80
6.66
6.52
6.69
6.54
6.51
6.50
6.49
6.30
195
647
848
1,514
4,516
9,853
11,654
13,481
10,236
5,237
443
.33
1.10
1.45
2.58
7.70
16.81
19.88
23.00
17.46
8.93
.76
169.42
169.81
169.29
170.19
170.22
170.71
170.57
170.51
170.25
170.33
169.41
6.27
6.96
7.02
6.86
6.88
7.13
7.23
7.05
6.98
6.96
7.30
2.99
2.71
3.15
1.60
1.24
.59
1.11
1.12
1.43
1.57
1.26
Occupation
White-Collar
Skilled
Farmer
Unskilled
No occupation
13,669
31,894
16,387
55,855
6,196
11.02
25.72
13.22
45.04
5.00
171.32
171.28
173.15
171.53
170.96
6.37
6.37
6.44
6.66
7.14
2,329
6,206
5,924
42,900
1,265
3.97
10.59
10.11
73.18
2.16
169.78
170.19
171.78
170.42
169.34
6.75
6.92
6.85
7.09
7.87
1.54
1.09
1.37
1.11
1.62
Nativity
North East
Middle Atlantic
Great Lakes
Plains
Southeast
Southwest
Far West
4,004
32,184
32,440
17,681
21,659
10,326
5,707
3.23
25.95
26.16
14.26
17.47
8.33
4.60
170.70
170.08
171.88
171.93
172.91
173.40
170.60
6.31
6.36
6.42
6.37
6.65
6.85
6.58
239
4,072
3,488
7,754
21,892
20,721
458
.41
6.94
5.95
13.22
37.34
35.35
.78
169.53
168.45
170.18
169.26
170.26
171.67
169.24
6.52
6.74
6.97
6.84
7.01
7.09
6.77
1.17
1.63
1.70
2.67
2.65
1.73
1.36
Source: See Table 1.
Notes: Stature is in centimeters. Youth age is between ages 15 and 22. The occupation classification scheme is consistent with Ferrie (1997); The following
geographic classification scheme is consistent with Carlino and Sill (2000): New England = CT, ME, MA, NH, RI and VT; Middle Atlantic = DE, DC, MD, NJ, NY,
and PA; Great Lakes = IL, IN, MI, OH, and WI; Plains = IA, KS, MN, MO, NE, ND, and SD; South East = AL, AR, FL, GA, KY, LA, MS, NC, SC, TN, VA, and WV; South
West = AZ, NM, OK, and TX; Far West = CA, CO, ID, MT, NV, OR, UT, WA, and WA. Stature difference is average white stature less average black stature.
across each of the states based on the hours of direct sunlight per day at county centroids in each state.7 Each state estimate
was then determined by summing the average hours of direct sunlight for each county (at its centroid), weighted by the proportion of the county’s total land area (in square miles) to the state’s total land area (in square miles). While this index is a rough
approximation for historical insolation, it provides sufficient detail to capture state latitudinal insolation variation and consequently, vitamin D production. Predictably, Southern states have greater insolation than Northern states. For example, Texas
receives 1.43, or 29%, more hours of direct sunlight per day than New York. It is also difficult to interpret insolation’s net direct
effect on human health, because greater insolation reduces calories required to maintain body temperature and produces more
vitamin D, but greater insolation also warms surface temperatures, which may have made disease environments less healthy
from water-born diseases, especially in the South (Steckel, 1992, p. 501).
3. The comparative effects of demographics, socioeconomic characteristics and insolation on black and white stature
Nineteenth century black and white biological conditions were related to age, birth cohorts, socioeconomic status, and nativity; they may have also been related to insolation, which is the primary determinant of vitamin D production. We test which of
these variables were associated with the height of nineteenth century black and white Americans. To start, stature for the ith
individual is assumed to be related with age, birth period, socioeconomic status, nativity, migration status, and insolation.
7
Insolation is not the insolation in the county that surround’s the state’s centroid, but insolation in each county’s geographic center. The range of state
insolation values extends from Maine’s minimum of 3.43 h of direct sunlight to Arizona’s maximum of 5.22 h of direct sunlight per day.
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S.A. Carson / Explorations in Economic History xxx (2008) xxx–xxx
Centimeteri ¼ b0 þ b1 Racei þ
70s
X
j¼12
þ
4
X
bj Agei;j þ
1900
X
t¼1800
bt Birthi;t þ
4
X
bl Occupationi;l þ
6
X
bn Nativityi;n þ bMig Migranti;Mig
n¼1
l¼1
2
bd MigrantDirectioni;d þ bInsol Insolationi;Insol þ BInsol2 Insoli;Insol þ bRaceInsol Race Insoli þ ei
d¼1
Dummy variables are included for individual youth ages 12 through 22; adult age dummies are included for ten year age
intervals from the 40s through the 70s. Birth decade dummies are in ten year intervals from 1800 through 1899. Occupation
dummy variables are for white-collar, skilled, farmers, and unskilled occupations. Nativity dummy variables are included for
birth in Northeast, Middle Atlantic, Great Lakes, Southeast, Southwest, and Far West regions. A dummy variable accounts for
migration status and directional migration dummy variables are included to account for North–South migrations.8 If insolation was a driving force in stature growth, northward moves will have adverse stature effects, and southward moves will be
associated with taller statures. Continuous insolation and insolation difference variables between receiving and sending locations are added to account for insolation and vitamin D production. Lastly, race and insolation interactive variables are included
to account for racial differences between how blacks and whites process vitamin D.
Table 3’s model 1 combines both blacks and whites, regressing height on observable characteristics and insolation. Model
2 negates migration effects by considering only blacks and whites who were incarcerated in their birth state. Model 3 regresses stature on only white male characteristics, while model 4 does the same for blacks. To account for how insolation
influenced stature differently by race, a black-insolation interactive variable is added to models 1 and 2, and a mulatto-insolation interactive variable is added to model 4.
Two general patterns emerge when comparing nineteenth century black and white statures. First, it is striking the degree
to which white stature exceeds black stature, which is significant because modern black and white statures are comparable
when brought to maturity under similar biological conditions (Eveleth and Tanner, 1976; Tanner, 1977; Steckel, 1995, p.
1910; Barondess et al., 1997, p. 968; Komlos and Baur, 2004, pp. 64, 69; Nelson et al., 1993, pp. 18–20; Godoy et al.,
2005, pp. 472–473; Margo and Steckel, 1982, p. 519; Komlos and Lauderdale, 2005). Moreover, compositional effects cannot
explain the white–black stature differential, which was due, in part, to whites’ access to meat and better nutrition (Margo
and Steckel, 1982, pp. 514–515, 517 and 519).
Second, consistent with the biomedical explanation, black and white statures responded differently with insolation. At
North American latitudes, black statures increased in insolation at an increasing rate, while white statures increased at a
decreasing rate, indicating there is a natural threshold to the amount of vitamin D produced internally, and whites in North
American latitudes were closer than blacks to the threshold where vitamin D production is curtailed (Holick et al., 1981, pp.
590–591; Jablonski, 2006, p. 62; Holick, 2004a, p. 363; Holick, 2004b, p. 1680S). Models 1 and 2’s negative and significant
black dummy variables indicate blacks were shorter than whites, and the positive black-insolation interactive term demonstrates that blacks at North American latitudes experienced larger stature gains from insolation than whites. Model 4’s positive and significant mulatto dummy variable indicates mulattos were taller than darker blacks, and the negative mulattoinsolation interactive term indicates darker blacks were more responsive than their mulatto counterparts to comparable
insolation levels. The black stature deficit may also be evidence of a previously neglected aspect of slavery’s consequences
on human biology: the forced migration of Africans to northern climates placed blacks into biological environments in
which, due to higher melanin levels in their skin, they were less likely to produce sufficient vitamin D and grow as tall as
whites (Loomis, 1967, pp. 501–504; Neer, 1979, p. 441).
Other patterns are consistent with expectations. Black and white statures varied considerably over the course of the nineteenth century (Fig. 2). Between 1830 and the eve of the Civil War, black statures increased by one-half cm (Komlos, 1992;
Komlos and Coclanis, 1997), supporting the Komlos–Rees hypothesis that Southern overseers followed a strategy to control
slave diets and health allocations to maximize slaveowner wealth (Rees et al., 2003; Komlos, 1998; Komlos and Coclanis,
1997; Hilliard, 1972). However, once US labor markets changed from a partially slave to a free labor force, the statures of
blacks born in the 1880s declined by one-half cm. Black statures increased by nearly 1 cm toward the end of the century,
despite economic and agricultural disruptions from the Boll Weevil and increased racial violence from whites (Higgs,
1977, p. 75). Alternatively, between 1800 and 1860, white statures declined by nearly 2 cm and stagnated throughout the
remainder of the nineteenth century.
During the nineteenth century, black and white statures varied by socioeconomic status, and farmers in the prison sample
were consistently taller than workers in other occupations (Metzer, 1975, p. 134; Margo and Steckel, 1982, p. 525; Steckel,
1979, p. 373). Farmers traditionally had greater access to superior diets and nutrition, but farmers also worked outdoors and
were exposed to more sunlight during adolescent ages; consequently, stature and socioeconomic status may also be related
8
North1 is an intermediate move from Southern to Central or Central to Northern states. North2 is a long distance move from Southern to Northern states.
South1 is a move from a Northern to Central or Central to Southern state. South2 is a move from Northern to Southern states. Northern states include Maine,
Vermont, New Hampshire, Massachusetts, Connecticut, Rhode Island, New York, New Jersey, Pennsylvania, Michigan, Wisconsin, Iowa, Minnesota, North
Dakota, South Dakota, Wyoming, Montana, Idaho, Oregon, and Washington. Central states include Delaware, Maryland, Virginia, Wes Virginia, Kentucky,
Indiana, Illinois, Missouri, Nebraska, Kansas, Colorado, Utah, Nevada, and California. Southern states include North Carolina, South Carolina, Georgia, Florida,
Alabama, Mississippi, Tennessee, Arkansas, Louisiana, Oklahoma, Texas, New Mexico, and Arizona. The binary variable North1 is an intermediate move from
Southern to Central or Central to Northern states. North2 is a long distance move from Southern to Northern states. South1 is a move from a Northern to Central
or Central to Southern state. South2 is a move from Northern to Southern states.
Please cite this article in press as: Carson, S.A., Geography, insolation, and vitamin D in nineteenth century US ..., Explor.
Econ. Hist. (2008), doi:10.1016/j.eeh.2008.09.002
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S.A. Carson / Explorations in Economic History xxx (2008) xxx–xxx
Table 3
National Stature Models related to Demographics, Birth Period, Migration, and Insolation by Socioeconomic Status.
Intercept
Race
White
Mulatto
Black
Model 1, Combined
SE
Model 2, Persisters
SE
Model 3, Whites
SE
Model 4, Blacks
SE
150.51***
2.28
116.20***
5.65
143.54***
2.49
174.03***
4.71
3.07***
Reference
.631
20.37***
16.43***
11.53***
8.40***
5.44***
3.32***
2.45***
1.38***
.452***
.291**
.163
Reference
.215***
.454***
.850***
1.56***
2.36***
1.50
.831
.530
.321
.193
.150
.126
.126
.122
.122
.113
.185
.645**
.204
.237
.454***
.007
Reference
.194***
.532***
.206*
.792**
.455
.284
.249
.194
.122
.093
Reference
Reference
Reference
3.46***
.350
1.80***
.455
Age
12
13
14
15
16
17
18
19
20
21
22
2329
30s
40s
50s
60s
70s
19.49***
16.11***
12.03***
8.34***
5.18***
3.23***
2.20***
1.19***
.554***
.223***
.075
Reference
.004
.402***
.892***
1.55***
2.30***
1.26
.783
.437
.252
.130
.093
.074
.069
.070
.067
.064
19.18***
17.37***
12.13***
8.58***
5.35***
3.13***
2.08***
1.21***
.536***
.279***
.146*
Reference
.051
.616***
..915***
1.20***
2.73***
1.46
.857
.490
.303
.167
.121
.098
.094
.095
.092
.090
Birth decade
1800s
1810s
1820s
1830s
1840s
1850s
1860s
1870s
1880s
1890s
1900s
1.32***
1.31***
.940***
.201***
.207***
.245***
Reference
.240***
.571***
.336***
.309
.197
.124
.102
.077
.057
.049
1.28***
1.56***
1.04***
.606***
.064
.277***
Reference
.217***
.551***
.324***
.541*
.348
.209
.172
.131
.092
.072
Occupations
White-Collar
Skilled
Farmers
Unskilled
.264***
.261***
1.10***
Reference
.055
.040
.049
.407***
.384***
1.00***
Reference
.088
.062
.068
Nativity
Northeast
Middle Atlantic
Great Lakes
Plains
Southeast
Southwest
Far West
1.20***
1.58***
.154***
Reference
.919***
2.75***
.101
.131
.093
.070
Na
1.17***
1.01***
Reference
.696***
4.23***
.657***
Migration status
Migrant
Non-Migrant
North1
North2
South1
South2
.454***
Reference
.856***
.766***
.390***
1.22***
.042
Sunlight
Insolation
Insolation2
10.75***
1.30***
1.08
.129
26.91***
3.23***
2.52
.285
.373***
.082
.062
.105
Insolation interaction
Black Insolation
Mulatto Insolation
N
R2
F
184,020
.0796
317.66
.042
.061
.093
.162
.351
.048
.056
.071
.238
.058
.110
.132
.065
.098
.155
.301
.707
.067
.077
.096
.309
.261
.182
.101
.178
.208
Reference
.060
.125
.054
.133
88,040
.1071
247.48
17.40***
15.32***
13.31***
8.35***
4.94***
3.16***
2.04***
1.10***
.620***
.182**
.036
Reference
.071
.352***
.850***
1.44***
2.03***
2.26
1.75
.751
.406
.171
.118
.091
.083
.085
.079
.077
1.46***
1.37***
1.11***
.270***
.151**
.335***
Reference
.265***
.591***
.417***
.168
.219
.138
.112
.084
.064
.057
.177***
.193***
1.21***
Reference
.060
.044
.056
.705***
.489***
.782***
Reference
.143
.093
.095
1.35***
1.76***
.071
Reference
1.02***
2.89***
.153
.141
.106
.079
.318
.959***
.945***
Reference
.887***
1.88***
.843**
.452
.184
.168
.365***
Reference
.907***
.688***
.384***
1.10***
.047
.092
.075
.177
.058
.144
.604***
Reference
.714***
.730***
.778***
1.84***
14.20***
1.75***
1.18
.141
3.02
.482*
2.24
.267
125,190
.0675
200.77
.160
.070
.105
.188
.417
.058
.070
.092
.316
.071
.138
.147
.082
.124
.202
.315
.629
.086
.093
.114
.356
.101
.200
.371
.103
.180
.151
.333
.145
.559***
58,830
.0926
116.42
(continued on next page)
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S.A. Carson / Explorations in Economic History xxx (2008) xxx–xxx
Source: See Table 1.
Notes: Because US historical insolation is unavailable, a modern insolation index (1993–2003) is constructed, and monthly insolation values are measured
from January thru June. The insolation index measures the hours of direct sunlight per day at county centroids in each state and is weighted by a county’s
square miles relative to square miles in the state.12 While this index is a rough approximation for historical insolation, it provides sufficient detail to capture
state latitudinal insolation variation and consequently, vitamin D production. The US geographic classification scheme is consistent with Carlino and Sill
(2000): New England = CT, ME, MA, NH, RI and VT; Middle Atlantic = DE, DC, MD, NJ, NY, and PA; Great Lakes = IL, IN, MI, OH, and WI; Plains = IA, KS, MN,
MO, NE, ND, and SD; South East = AL, AR, FL, GA, KY, LA, MS, NC, SC, TN, VA, and WV; South West = AZ, NM, OK, and TX; Far West = CA, CO, ID, MT, NV, OR, UT,
WA, and WA. *** Significant at .01; **Significant at .05; *Significant at .10.
to vitamin D production (Bodiwala et al., 2003, pp. 659–660; Tangpricha et al., 2002, p. 662; Holick et al., 1981, p. 590). Islam
et al. (2007, pp. 383–388) demonstrates that children exposed to more direct sunlight produce more vitamin D, and if there
was little movement away from parental occupations, nineteenth century occupations may also be a good indicator for the
occupational environment in which individuals came to maturity (Costa, 1993, p. 367; Margo and Steckel, 1992, p. 520;
Wananamethee et al., 1996, p. 1256–1262; Nyström-Peck and Lundberg, 1995, pp. 734–737).9 That unskilled workers were
also tall suggests that many unskilled workers were agricultural workers, who received sufficient nutrition allocations and almost certainly worked outdoors, receiving more insolation to produce sufficient vitamin D, and reached taller terminal statures.
Black and white statures varied regionally, and after controlling for insolation, Southern blacks and whites reached the
tallest statures. Moreover, internal immigrants who located to the South were taller than those who immigrated to the
North, and Southern black stature gains were larger than those experienced by whites. Part of the Southern migration advantage was related to Southern agriculture. The nineteenth century opening of the New South to agriculture increased Southwestern agricultural productivity, which was higher than elsewhere in the US (Higgs, 1977, p. 24; Margo and Steckel, 1982,
p. 519; Komlos and Coclanis, 1997, p. 443). Before the Civil War, the South was self-sufficient in food production, and relatively high wages for whites may have also influenced Southern white statures (Fogel, 1994, pp. 89, 132–133). After the Civil
war, Southern wages in the West South Central were in general lower than Midwest wages and were comparable to those in
the middle Atlantic region. Blacks from the Great Lakes were taller than blacks from the Northeast and Plains. The relative
price of dairy and calcium were lowest in dairy producing regions, such as Great Lake states, but nineteenth century blacks
were overwhelmingly native to the South.10 Northeastern blacks, especially youth, encountered adverse biological environments, and contemporary reports of rickets—a result of vitamin D deficiency—may have contributed to shorter Northeastern
black and white statures (Kiple and Kiple, 1977, pp. 293–294; Tortolani et al., 2002, p. 62).
4. Explaining the relative white stature advantage
To more fully account for the source of the white–black stature differential and to isolate the relative importance of insolation, I compute the Blinder–Oaxaca decomposition on the white–black stature differential (Oaxaca, 1973). I also calculate
how much of the stature gap between blacks born in Africa to blacks born in North America may have been due to insolation
differences.
Let Sw and Sb represent the statures of whites and blacks, respectively; aw and ab are the autonomous stature components
that accrue to whites and blacks; bw and bb are the white and black stature returns associated with specific stature enhancing
characteristics, such as age and occupation. Xw and Xb are white and black characteristic matrices, and white statures are
assumed to be the base structure.
DS ¼ Sw Sb ¼ ðaw ab Þ þ ðbw bb ÞX b þ bw ðX w X b Þ
The second right hand-side element is that component of the stature differential due to differences in stature returns and
for most characteristics was likely positive. Hence, if white stature advantages were due to inferior black biological conditions, the stature returns to whites, bw, will be larger than stature returns to blacks, bb. If, however, blacks at North American
latitudes received larger relative stature gains than whites, the returns to the stature gap from insolation will be negative.
The third right-hand side element is the stature differential component due to differences in characteristics and is undetermined because whites probably had characteristics associated with taller statures, but blacks lived in the South with greater
exposure to insolation.
Using coefficients from the stature regressions (Table 3, models 3 and 4), the stature decomposition indicates that the
majority of the white stature advantage arose from non-identifiable characteristics, such as better nutrition and higher
socioeconomic status that disproportionately favored whites (Table 4); however, the majority of the stature differential
due to observable characteristics is associated with insolation. Measured in levels, the share of the stature gap attributable
to characteristics illustrates that nineteenth century blacks lived in areas that received more insolation.11 Measured in pro-
9
Modern studies also demonstrate that rural African women who work outdoors produce more vitamin D than urban women (Nesby-O’Dell et al., 2002, p.
189). Holick et al. (1981, p. 590) also illustrates that the amount of exposure to sunlight is the most significant factor in vitamin D production.
10
Southern observers at the time reported that milk was fairly abundant in border states but in short supply in the Deep South (Kiple and King, 1981, p. 83).
11
Blacks in the prison sample lived in states that received 4.37 h of direct sunlight per day compared to whites in the sample who lived in states that received
3.95 h of sunlight per day, or blacks lived in states that received about 11 percent more insolation than whites.
12
Insolation is not the insolation in the county that surround’s the state’s centroid, but insolation in each county’s geographic center. The range of state
insolation values extends from Maine’s minimum of 3.43 hours of direct sunlight to Arizona’s maximum of 5.22 hours of direct sunlight per day.
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S.A. Carson / Explorations in Economic History xxx (2008) xxx–xxx
167
171.5
172
168
172.5
169
173
170
173.5
174
Whites
171
Blacks
1800
1820
1840
1860
1880
1900
1800
Year
National Black
1820
1840
1860
1880
1900
Year
Northern Black
Southern Black
National White
Northern White
Southern White
Fig. 2. Nineteenth century regional black and white stature by nativity (See Table 1. Notes: African-American and white stature graphs made from national,
northern and southern models not presented here from Table 3. To simplify graphs, youth and adult age groups are combined, and insolation was not
included in these models. Northern states are MN, IA, WI, MI, IL, IN, OH, PA, NJ, NY, CT, RI, MA, NH, VT, and ME. Southern states are AL, AR, FL, GA, KY, LA, MO,
NC, TN, TX, and SC.)
Table 4
Nineteenth century national prison stature Oaxaca decomposition.
Levels
ðbW bB ÞX B
bW ðX W X B Þ
Total
Sum
1.76
56.40
54.64
Proportions
Intercept
Ages
Birth
Occupations
Nativity
Migration
Insolation
Sum
Total
.558
3.64
7.44
1.83
5.43
2.63
.586
.032
1.74
3.46
.9.34
9.04
2.33
1.04
1.03
1
Source: See Tables 2 and 3.
portions, black returns to insolation at North American latitudes were greater than whites. Observable characteristics beyond
insolation did not contribute to the white–black stature differential. Therefore, at North American latitudes, black stature gains
from insolation were larger than for whites, and blacks lived in states that received more insolation; however, the majority of
the white–black stature differential is explained by non-identifiable characteristics, such as differences in access to nutrition,
overt forms of racial prejudice, and economic exclusion.
We can also assess the biological penalty imposed on blacks as a result of their forced migration from African to North
American latitudes. Holding all other variables constant and assuming nineteenth century nutrition and medical conditions
were comparable between Africa and North America, the stature of 20 year old unskilled blacks observed at African insolation (5.60 h) is 172.23 cm. The stature of 20 year old unskilled blacks at North American insolation (4.36 h) is 170.02 cm, or
African blacks had average statures that were 2.21 cm taller than blacks brought to maturity under North American insolation. If blacks and whites reach similar statures when brought to maturity under comparable biological conditions, Table 3’s
model 1 indicates the nineteenth century black to white stature penalty was 3.50 cm. Therefore, over 50% (2.21/3.50 = .63) of
Please cite this article in press as: Carson, S.A., Geography, insolation, and vitamin D in nineteenth century US ..., Explor.
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S.A. Carson / Explorations in Economic History xxx (2008) xxx–xxx
the nineteenth century stature differential between blacks born in Africa versus North America may be attributable to inefficient black vitamin D production at North American latitudes.
5. Conclusion
This paper identifies insolation as an important source for nineteenth century black and white statures and illustrates that
at North American latitudes the two groups responded differently to the effects of insolation and vitamin D. Although modern blacks and whites are more likely to come to comparable statures when brought to maturity under similar biological
conditions, nineteenth century US blacks were ubiquitously shorter than their white counterparts. As reported elsewhere,
mulattos had a stature advantage over their darker black counterparts (Steckel, 1979; Bodenhorn, 1999 and 2002; Margo
and Steckel, 1992, p. 511), which persists after controlling for insolation. Moreover, there is a biological threshold to vitamin
D production, and whites in North America were closer than blacks to the threshold where vitamin D production is curtailed.
Part of the black stature deficit may have also been due, in part, to blacks’ forced migration to northerly latitudes, where, due
to higher melanin levels in their skin, blacks were less likely to produce sufficient vitamin D and grow as tall. For example,
Africans are biologically suited for maximum stature growth on or near the equator, and while it is not possible to identify
the origins of slaves completely, African insolation is significantly greater than North American insolation, and over 50% of
the stature differential between blacks born in Africa and North America may be explained by insolation differences.
The stature-insolation hypothesis also adds to our knowledge for why nineteenth century farmers were taller than workers in other occupations. Farmers were undoubtedly closer to nutritious food supplies and farther from crowded urban locations, where disease was most easily propagated. However, farmers were also exposed to more sunlight, produced more
vitamin D than their white-collar and skilled counterparts and reached taller terminal statures. Therefore, rather than only
sociological processes and access to nutrition explaining the stature difference between blacks and whites, part of the difference may be biologically based.
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Please cite this article in press as: Carson, S.A., Geography, insolation, and vitamin D in nineteenth century US ..., Explor.
Econ. Hist. (2008), doi:10.1016/j.eeh.2008.09.002