The Proximate Determinants of Fertility in Sub-Saharan Africa
Author(s): John Bongaarts, Odile Frank and Ron Lesthaeghe
Source: Population and Development Review, Vol. 10, No. 3 (Sep., 1984), pp. 511-537
Published by: Population Council
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Data and Perspectives
The Proximate
Determinants of Fertility
in sub-Saharan Africa
John Bongaarts
Odile Frank
Ron Lesthaeghe
As measuredby mostconventional
indicators
of socioeconomicdevelopment,
sub-SaharanAfricaremainstheleastdevelopedregion
oftheworld.Whilestandards
oflivinginthepoorestcountries
ofLatinAmerica
and Asia, on average,have been rising,theyactuallydeclinedin the lowincomecountries
ofAfricaduringthe1970s,whenpopulation
growth
exceeded
thesmallriseinoveralleconomicoutput.Evenifthisadversetrendis reversed
inthecomingdecade,itis likelythatlargepartsofsub-Saharan
Africawillnot
be muchbetter
offthantodayfortheforeseeable
future.
These factshavecaused increasing
concernamongAfricangovernment
as well as in international
officialsand policymakers
agenciesthatdeal with
issues.However,despitetheimportant
rolerapidpopulation
development
growth
has likelyplayedinproducing
thepooreconomicconditions,
fewgovernments
haveexpressedconcerninthepastaboutdemographic
Measures
developments.
to reducerapidpopulationgrowthsuchas thoseadoptedby numerous
Asian
and LatinAmericancountrieshave been absentin sub-SaharanAfrica.This
situationis now clearlychangingand the searchis underway foreffective
in orderto effecta declinein theratesof
policiesto reduceexcessivefertility
forAfrica,1984).
population
growth
(UnitedNationsEconomicCommission
The designand implementation
of such policieswouldgreatlybenefit
froma detailedunderstanding
of thesocioeconomic,cultural,biological,and
environmental
factorsthatdetermine
Thispaperseekstocontribute
to
fertility.
suchunderstanding
an assessment
oftheproximate
by providing
determinants
offertility
levelsanddifferentials
fortheregion.
The demographic setting
torecentUnitedNationsestimates,
sub-Saharan
Africa'hadapproxAccording
in 1980(UnitedNations,
imately338 millioninhabitants
livingin 37 countries
POPULATION
AND DEVELOPMENT
REVIEW
10, NO. 3 (SEPTEMBER
1984)
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511
Fertility
512
Determinants
in sub-Saharan
Africa
Nigeria(77
1982). Overhalfthepopulationlivedin thefivelargestcountries:
million),Ethiopia(32 million),Zaire (28 million),Sudan (18 million),and
shareof theworld'spopulationinTanzania(18 million).The subcontinent's
creasedfrom6.2 percentin 1950to 7.6 percentin 1980.
of sub-SaharanAfricaare uniquebeThe demographic
characteristics
anditsbirthanddeathratesareall higher
cause thepopulation'srateofgrowth
unexpected
thanin any othercontinent
or majorregion.This is notentirely
moredevelopedandhencehas
sincemuchoftherestoftheworldis relatively
however,
transition.
It is surprising,
intothedemographic
progressed
further
indicators
is stillfoundif
thata substantial
discrepancy
betweendemographic
(usingtheWorldBank's
countries
one restricts
to low-income
thecomparison
in 1980had an annualpercapitaGNP below
countries
definition,
low-income
$420; WorldBank, 1982). The relevantdata are plottedin Figure1. For the
Africa and in
FIGURE 1 Vital rates in sub-Saharan
low-income countries of Asia and Latin America
Birthand death rates
50
SUB-SAHARAN AFRICA
BIRTH RATE
40_
c; 30_-_
O1Z.
o)
20
ASIA AND LATINAMERICA
_
DEATH RATE
- - _SUB-SAHARAN
- - _
AFRICA
10
ASIA AND LATIN AMERICA
0
1950
l
l
1960
1970
1980
1970
1980
Populationgrowthrates
3
SUB-SAHARAN AFRICA
C
-
-AIAAS
AND LATINAMERICA
C-
0
1950
1960
SOURCE: UnitedNations(1982).
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John Bongaarts
/ Odile Frank
/ Ron Lesthaeghe
513
period1975-80 thebirthand deathratesof low-incomesub-SaharanAfrica
were48 and20 perthousand
respectively,
yieldingan annualpopulation
growth
rateof2.8 percent.Thesefigures
arevirtually
thesameforsub-Saharan
Africa
as a whole.In contrast,
thelow-incomecountries
of Asia and LatinAmerica
hada birthrateof29, a deathrateof 11,anda growth
rateof 1.8 percent.These
statistics
fornon-African
countriesare heavilyinfluenced
by theremarkable
declinesinfertility
andmortality
thathaveoccurred
inChina,buteven
recently
showninFigure1 wouldnotdisappear.
ifChinais excluded,thediscrepancies
Anothernotablefeatureof Figure 1 is the difference
in demographic
trendsbetweencontinents.
The birthratein sub-Saharan
Africais stablewhile
ithas beendecliningelsewhere.In fact,duringthe1970sthebirthratein lowincomeAsia and LatinAmericadeclinedfasterthanthedeathrateso thatthe
growth
rateis nowalso declining.This is notthecase in Africa.The constant
birthrate,combinedwithmodestreductions
inthedeathrate,has resultedina
populationgrowthratethatis higherthanever and stillrising.As a consequence,thepopulationof sub-Saharan
Africais expectedto reach627 million
in theyear2000 and 1.17 billionin 2025 (UnitedNations,1982). Of course,
somecountries
willgrowevenfaster.Kenya,forthemoment
theworld'srecordholder
withan annualgrowthrateof 4 percent,is projectedto growfrom
16.5 millionin 1980to 82.3 millionin 2025, a fivefold
increase.
Fertility levels and differentials
The overalllevel of fertility
in sub-SaharanAfricaas measuredby thetotal
rateis approximately
6.6 birthsper womanfortheperiod1975-80
fertility
(UnitedNations,1982). Thisestimateis an averagethatconcealsconsiderable
variationin nationalfertility
levels. In general,fertility
is highestin theeast
and thewestand lowestin thecentralregions(in Gabon,Cameroon,Central
African
Republic,andpartsofSudan,Zaire,andCongo).Thetotalfertility
rate
rangesfroma highof8.1 inKenyato4.1 inGabon.Whilethisis an impressive
infertility
range,itis notunusual:similarvariations
arefoundinAsia andLatin
America.However,Africais uniquein thatthelowestlevelsof fertility
have
notbeen achievedthrough
declinesin fertility.
Countrieswithrelatively
low
in
fertility LatinAmericaand Asia haveexperienced
rapiddeclinesin fertility
thatare correlatedstrongly
withsocioeconomicdevelopment
and organized
efforts
to reducethebirthrate.In contrast,
in sub-Saharan
no country
Africa
has experienced
a significant
reduction
in fertility,
and thereis no correlation
betweendevelopment
indicators
and fertility.
The processesthatgive riseto
in sub-SaharanAfricaare therefore
differentials
fertility
from
verydifferent
thosefoundelsewhere.
In addition
infertility
tovariation
betweennations,therearelargefertility
differences
bygeographic
regionandbyethnicandsocioeconomic
groupswithin
countries.Figure2 offersa fewexamples.The upperpartof thefigureshows
thatthetotalfertility
ratein Cameroonis 50 percent
higherin theWestthanin
theSoutheast.Similarandsometimes
evenlargerregionalorethnicdifferences
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514
Fertility Determinants
in sub-Saharan
Africa
in fertility
have been foundin otherAfricancountries(Frank,1983b). The
lowerpanelsofFigure2 demonstrate
thatbettereducatedandurbanwomenin
generalhave lowerfertility
thantheirunschooledand ruralcounterparts.
It
shouldbe emphasized,however,thatmoreeducationor an increasein literacy
is notnecessarily
associatedwithlowerfertility.
Thus,forexample,thetotal
rateof womenwithno schoolingis lowerthanthatof womenwith
fertility
1-3 yearsof schooling(Figure2, middlegraph).This has veryimportant
implicationsbecause thelargemajority
of womenfall in thesetwo categories.
Thissubjectwillbe addressedin greater
detaillater.
FIGURE 2 Examples of fertility differentials by region
and by level of schooling and urbanization in subSaharan Africa
REGIONAL DIFFERENCES
IN CAMEROON
WEST
NORTH
SOUTHEAST
EDUCATIONAL DIFFERENCES
(AVERAGE OF FIVE COUNTRIES)'
NO SCHOOLING
1-3
YEARS
4-6
YEARS
7+ YEARS
URBAN/RURAL DIFFERENCES
(AVERAGE OF FIVE COUNTRIES) a
RURAL
URBAN
0
2
4
6
8
Total fertilityrate
a Educationand place of residenceof womenin theWorldFertility
Survey
samplesof Ghana,Kenya,Lesotho,Senegal,and Sudan.
SOURCE: Frank(1983b) and Casterlineet al. (1983).
Even greatervariationin fertility
is foundamongindividualwomen.In
all sub-Saharan
African
forwhichindividual-level
countries
measuresareavailable, thenumberof childreneverbornamongwomenat theendof thereproductiveperiodrangesfrom0 to 14 or more. Figure3 illustrates
thiswith
observations
fromKenyaand Ghana. AlthoughKenya's totalfertility
rateis
substantially
higherthanGhana's (8.1 vs. 6.7), thetwodistributions
of comofindividual
pletedparities
womenoverlaptoa largeextent.As a result,a large
ofwomeninKenyahavesmallerfamiliesthantheaverageGhanaian
proportion
womanand,similarly,
theaverageKenyanfamilysize is exceededbythefertilityofa substantial
proportion
ofGhanaianwomen.
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/ Odile Frank
John Bongaarts
515
/ Ron Lesthaeghe
FIGURE 3 Distribution of number of children ever
born among ever-married women aged 45-49 in
Kenya (1977) and Ghana (1979)
20
-a15
2
Uo
I
0
Ulo
E
>
0.)
0
(U
0
0
10
5
15
Numberof childreneverborn
SOURCE: Republicof Kenya(1980) and Republicof Ghana(1983).
Clearly, variationsin national,subnational,and individuallevels of fertilityin sub-SaharanAfricaare large. This is all themoreremarkablesince only
through
a very small percentageof women deliberatelycontroltheirfertility
contraceptionor induced abortion.Explanationsforthese findingsmustthereforebe foundlargelyelsewhere. This is thetask we turnto next.
The determinants
of fertility
fertility
requires
Anydetailedand comprehensiveanalysisof factorsinfluencing
thata distinctionbe made betweentwo classes of determinants:
(1) proximate
variables and (2) socioeconomic and environmental"background" variables.
The latterinclude the social, cultural,economic, institutional,psychological,
consistof
health,and environmentalvariables,and theproximatedeterminants
all biological and behavioral factorsthroughwhich the backgroundvariables
mustoperate to affectfertility
(Davis and Blake, 1956; Bongaartsand Potter,
of a proximatedeterminant
is itsdirectinflu1983). The principalcharacteristic
variables
can
socioeconomic
affect
In
ence on fertility. contrast,
fertility
only
indirectlyby modifyingtheproximatedeterminants.
Socioeconomic
and
environmental
vaibe
(be.g.,education,(e.g.,
education,age
(eai;h)
'I
P
droinats
determinants
contraception,
at marriage)_
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Fertility
516
Fertility Determinants
in sub-Saharan
Africa
One of themostimportant
advantagesof includingtheproximate
variablesinthestudyofthefertility
processis thatitimproves
ofthe
understanding
In generala socioeconomic
ofthesocioeconomic
determinants.
operation
varione setof proximate
effectsthrough
able can have negativefertility
variables
on use ofcontraception)
andpositiveeffects
(suchas education'seffect
through
The overall
anotherset(suchas education'seffecton lengthofbreastfeeding).
can therefore
neteffectof a socioeconomicvariableon fertility
be positive,
on therelativecontributions
ofthepositive
negative,orinsignificant
depending
oftheproximate
determinants.
Theseoffsetting
effects
of
andnegativeeffects
on fertility
levelsplayan especiallycrucialrolein subproximate
determinants
thissubjectfurther,
it is necessaryto
SaharanAfrica,butbeforeconsidering
in somedetail.
discusstheproximate
determinants
is a completelistand a briefdescription
The following
oftheproximate
determinants:
Proportion
ofwomenmarriedor insexualunionsThisvariablemeasures
the degreeto whichwomenof reproductive
age are exposedto the riskof
conceiving.
Frequencyof intercourseThis determinant
directly
affectstheprobabilityof conceivingamongovulatingwomen.Frequentor prolongedspousal
has therefore
a substantial
separation
effect.
fertility-reducing
Postpartum
abstinence Prolonged
fromsexualrelations
abstinence
while
is commonin a numberof societies,manyofthem
a newbornis breastfeeding
in Africa.
Lactationalamenorrhea Followinga pregnancy
a womanremainsunable to conceiveuntilthenormalpattern
of ovulationand menstruation
is restored(postpartum
amenorrhea).
Whenbreastfeeding
takesplace,theduration
of lactationalamenorrhea
is primarily
determined
by theduration,intensity,
andpattern
ofbreastfeeding.
ContraceptionAnypracticeundertaken
toreducetheriskof
deliberately
is considered
ifitsaimis to limitfamilysize. Breastconception
contraception
feedingand postpartum
abstinence,whiletheyaffectfertility
by increasing
childspacing,arenotincludedas contraception
becausetheiraimis primarily
the
of maternal
protection
healthand childdevelopment
ratherthanregulation
of
thenumber
ofchildren
born.2
Inducedabortion Thisincludesanypracticethatdeliberately
interrupts
thenormalcourseofgestation.
Spontaneousintrauterine
ofall conceptions
mortalityA proportion
fail
to end in a live birthbecause somepregnancies
spontaneously
terminate
preina miscarriage
or stillbirth.
maturely
NaturalsterilityOnly a smallproportion
of womenare sterileat the
ofthereproductive
beginning
years,butthisproportion
increaseswithage and
reaches100percent
byage 50.
PathologicalsterilityA numberofdiseases,especiallygonorrhea,
can
cause primary
or secondarysterility.
Primary
sterility
resultsin childlessness
becausea sterilizing
diseaseis contracted
beforea first
birth.Secondarysterility
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John Bongaarts
/ Odile Frank
/ Ron Lesthaeghe
517
resultsin an inability
to bearadditionalchildren,sometimes
veryearlyin the
childbearing
years,andis duetotheonsetofdiseaseamongwomenwhoalready
haveborneoffspring.
The importance
ofeach of theseproximate
variablesin determining
ferin sub-Saharan
tilitydifferentials
Africarangesfrommajor(lactationalamenorrhea,postpartum
abstinence,and pathologicalsterility)to insignificant
(spontaneous
abortion
andnaturalsterility).
The reviewoftheproximate
determinants
providedinthenextsectionhighlights
therelativeimportance
ofthese
.3
variables
The proximate determinants
reproductive behavior
and
The highand constantlevel of fertility
in sub-Saharan
Africaoveralland the
oftenlargedifferences
thatit subsumesmustin the end be explainedby a
groupof characteristics,
behavioraland biological,thatdirectlydetermine
theircombinedeffects.The behavioralcharacteristics
fertility
through
include
of sexual activity,durationof breastfeeding,
marriagepatterns,
patterns
and
use of birthcontrolthroughcontraception
and inducedabortion,whilethe
biologicalcharacteristics
includefetalloss and bothnaturaland pathological
sterility.
Patterns
of marriage and sexual
unions
a womancouldinprinciple
Although
bearchildren
herreproductive
throughout
life,fromtheage of about15 to about45, thisis rarelythecase, becauseher
overallexposureto childbearing
is limitedto the totalamountof thattime
duringwhichshe is actuallycohabiting
or in a union(forsimplicity,
theword
"marriage"as usedheredenotesanysuchregularsexualunion).In anysociety,
thetotaltimespentinunionsforall womendependson theage atfirst
marriage,
the proportion
of womenwho nevermarry,the frequency
of divorceand
of remarriage,
widowhood,thefrequency
andtheage at whichsexualactivity
comesto an end (if thisoccursbeforemenopause).These variousfactorsare
summarized
of all womenmarriedat anypointin time.In
by theproportions
theroleof marriagein limiting
considering
theexposureof womento childsome
also
be
accountmust
takenofthelevelofextramarital
bearing,
exposure,
by youngwomenbeforemarriageand by oldernever-married
and unmarried
(divorcedandwidowed)women.Finally,evenwithinmarriage,
theparticular
formsit takescan affectthe translation
of marriageintoexposureto childbearing,principally
throughthe patternsof sexual activitythattendto be
associatedwithit. Forexample,arranged
tendto be associatedwith
marriages
lowerfrequencies
of intercourse
thanromantic
marriages
(Rindfussand Morgan, 1983), and polygynous
tendalso to be associatedwithlower
marriages
sexualactivity(of each woman)thanmonogamous
ones.
All themarriagefactorshave relevancein theAfricancontext,and of
theformsof marriage,polygyny
is themoreimportant
to theexplicationof
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518
Fertility Determinants
in sub-Saharan
Africa
in sub-SaharanAfrica.The role of polygyny,
fertility
however,will be discussedunderpatterns
of sexualactivity.
Age atfirstmarriageThe averageage at whichwomenentertheirfirst
unionvariesregionallyfrombelow 17 yearsto around22. Overall,age at
is at thelow endoftherangein westAfrica,at thehighendin parts
marriage
incentralAfricaandinthecoastalareasaround
ofeastAfrica,andintermediate
theBightof Beninand theGulfof Guineain thewestand theIndianOcean
in the east (see Figure4). Age at marriageis higherin urbanthanin rural
areas,in associationwithhigherlevelsof educationforurbanwomen.
in age at first
seemtoreflect
Thesedifferentials
truedifferences
marriage
in regionaland ethnicpracticesratherthana cross-sectional
pictureof a conin theage at first
sincethereis littleevidencethat
tinental
transition
marriage,
increasedinAfrican
nationalpopulations
has substantially
over
age atmarriage
thelast20 or 30 years.An exceptionto thisis Kenya,whererelatively
better
dataat severalpointsin timeshowtheaverageage at firstmarriage
risingby
morethana yearand a half,fromjustover 18.5 to over20 between1962 and
1979. It is also possiblethatnorthern
Sudan has experiencedsome increase
in theaverageage at firstmarriage.
The sub-SaharanAfricanrangeof age at firstmarriageis somewhat
lowerthantherangein Asia as measuredby theWorldFertility
Surveysin
in two otherimportant
themidto late 1970s,butthetworegionsalso differ
size has as earlyan age
respects.First,no Africanpopulationof significant
at first
as Bangladeshin 1975 (about16 years).Second,dataforthe
marriage
large majorityof Asian countriesshow thatcurrentlevels of ages at first
marriageresultfromfairlywidespreadincreasesin age at marriagesince
the 1950s.
Theproportion
of womenwho nevermarryMarriageis forall intents
of womenstill
Africa.The proportion
and purposesuniversalin sub-Saharan
is alreadyonlyaround5 percentor less in theage group25-29,
unmarried
The proportions
of womenwho
and declinesto 3 percentor less thereafter.
thedistriare singlein theyoungestage groupsin Africathusmerelyreflect
butionaroundthe averageage at entryintotheirfirstmarriageand bear no
of permanent
to theverylow probabilities
relationship
celibacy.
Thefrequencyof divorce,widowhood,and remarriageMaritalinstadissolution(divorce)and involuntary
dissolution
bilitydue to bothvoluntary
Africabyanystandard.
sub-Saharan
(widowhood)is highthroughout
However,
veryhighratesofremarriage
andgood accessibility
to husbandsthrough
polygynymeanthatfewwomenare notin unionsat anypointin timerelativeto
the incidenceof marriagedissolutions.A standardscheduleforsix African
of firstmarriagesendingin divorce
countriesshowstheaverageproportions
or widowhoodby durationof thefirstmarriageforwomencurrently
below
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Female
4
FIGURE
age
recent national
data
at first marriage
in sub-Saharan
(years)
Africa,
most
Youngerthan16.7yearsTUIA
16.7to 17.9years
18.0to 19.6years
DJIBOU_TI
19.7yearsorolder
ALGERIA
SIERRA LEON
A
BURKI
GAMBI
GUINEA BISSAU
GiNEA
FA
LBYAEGV
N
REPUBIC
\
MAURINA
CBN
URNTANI
3E
BISSAUINEDA
&UINEA
ELILIBERI
G
8
SUDAN
A
ZI
C
SUDN
ANA
LIBRIIHANIAMBO
SOUTH AFRICA
SOURCES: Lesthaeghe(I984); Locoh (1982); Kingdomof Lesotho(1981);
FederalRepublicof Nigeria(1983).
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A
ALA
NDAS
yAAN60L
O
DJMOZAMBIQ E
MADAGASCAR
SWAZILAND
LESOTHO
520
Fertility Determinants
in sub-Saharan
Africa
age 50. The schedule,givenin Table 1, showsthattheproportion
ofwomen's
firstmarriagesendingin divorcerangesfromover 7 percentforveryshort
durations
(0 to 4 years)to nearly20 percentforthelongestdurations
(30 or
moreyears).The incidenceofwidowhoodis muchlowerforshorter
durations
(whenhusbandsare youngerand have lowermortality),
butincreasesrapidly
and reachesthe incidenceof divorcein the longestdurationsof marriage.
Amongwomenmarried
less thanfiveyears,some8 percenthaveexperienced
theend of a firstunion,eitherthrough
divorceor widowhood;amongwomen
married30 yearsor more,theproportion
is 40 percent.For all durations
of
firstmarriageexcept30 or moreyears,whichessentiallyappliesto women
pastchildbearing,
divorceis by farthemajorcause of dissolution,
and would
therefore
be themajorreasonforanytimelostto childbearing
associatedwith
an unmarried
state.
TABLE 1 Percent of first marriages ending in divorce, widowhood,
and both by years since first marriage for women aged 15-49:
average for 6 African countries,a 1977-79
Years since firstmarriage
Divorce
Widowhood
Divorceand widowhood
0-4
5-9
10-14
15-19
20-24
25-29
30+
7.4
0.8
8.2
13.9
2.1
16.0
16.7
4.6
21.3
17.1
8.0
25.1
18.0
11.5
29.5
18.3
15.0
33.3
19.5
21.0
40.5
a
Cameroon,Ghana,Kenya,Lesotho,Senegal,Sudan.
SOURCE: Lesthaeghe(1984).
As a resultof highratesof remarriage,
however,comparatively
few
womenare in factcurrently
widowedor divorcedat anytime.For thesame
six countries,
only5 to 10 percentof womenaged 20-39, theentirerangeof
peak childbearing
years,will be foundunmarried
at any time.Takinginto
accountdissolution
of first
and of subsequentmarriages,
afterfirst
remarriage
and subsequentdissolutions,and considering
all formsof conjugalunions,
oncetheyentertheirfirst
union,womenin sub-Saharan
Africawillspendover
90 percentof theirremaining
lifein a union(see Table 2).
reproductive
TABLE 2 Percent of all women currently widowed or divorced and
mean percent of time since first marriage spent in sexual union by
ever-married women by age: average for 6 African countries,a
1977-79
Age group
Percentcurrently
widowedor divorced
Percentof timespentin
sexualunion
15-19
20-24
25-29
30-34
35-39
40-44
45-49
2.4
5.1
5.6
7.7
10.3
13.9
n.a.
96.8
95.6
95.2
94.2
93.7
92.7
91.4
n.a. = notavailable.
a For
see noteto Table 1.
countries,
SOURCE: Same as Table 1.
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John Bongaarts
/ Odile Frank
/ Ron Lesthaeghe
521
Overtime,theincidenceof widowhoodhas probablydeclinedsteadily
The risksof widowhoodamongAfricanwomen
withreducedadultmortality.
declinesat earlierages of womenthanin many
are moresensitiveto mortality
betweenspousesare
otherregionsof theworld,because theage differences
large(van de Walle, 1968). Forexample,themedianage gap ranges
typically
womenmarriedless than
fromaboutsix to eightyearsforall once-married
tenyears,up to 15 to 20 yearsand moreforthosewomenwho are second
unions(Casterlineand McDonald, 1983). With
andthirdwivesinpolygynous
the incidenceof divorce,which
reductionsin adult mortality,
any further
determine
willincreasingly
alreadyplaysthemajorrolein maritaldissolution,
incidenceof remarriage
whilethecurrent
theincidenceof maritaldissolution,
womenat a verylow
of unmarried
will continueto maintaintheproportion
level.
outsidemarriage,
ExposureoutsidemarriageExposureto childbearing
beforefirstmarriage,is appreciablein Africa,and mustbe conparticularly
as represented
by
sideredalongsidewomen'sformalexposureto childbearing
the portionof theirlives duringwhichtheyare in one or anotherformof
exposurevariesconconjugalunion.However,theincidenceof extramarital
itslevelfortheentire
tocharacterize
itis therefore
difficult
Although
siderably.
region,it is probablethataround5 to 10 percentof all birthsare contributed
women(Lesthaeghe,1984).
by unmarried
theroleof Africanmarriagepatterns
one can characterize
In summary,
as follows:womenmarrywell aftertheirreproductive
in relationto fertility
years,they
all marryby thepeak childbearing
lifehas begun,theyvirtually
experiencehighratesof divorceand appreciablewidowhood,but remarry
are in some formof conjugalunion
enoughthatthevastmajority
frequently
to
restricted
is notentirely
theirchildbearing
years.Childbearing
throughout
of all birthsoccurto women
unions,however,and an appreciableproportion
whenunmarried.
Patterns
of sexual
activity
was important
In theprevioussection,we saw howtotaltimespentin marriage
Duration
womancouldbearchildren.
inassessingtheamountoftimea married
of marriedtime,however,is notnecessarilyequivalentto thetotalduration
exposureto pregwithinmarriage.Withinmarriage,
ofexposureto pregnancy
nancydependson the patternof sexual activity.The threemostimportant
of spouses,abof intercourse
duringcohabitation
factorshereare frequency
of
and
spouses.
separation
spouses,
stinencebetweencohabiting
Thereis strongevidencethatrealdifferences
Frequencyof intercourse
are associatedwithmarriageforms.Thus polygynously
in coital frequency
married
women,and
thanmonogamously
womenhavelowerfertility
married
determinant.
is probablyone important
Polyof intercourse
lowerfrequency
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522
Fertility Determinants
in sub-Saharan
Africa
notonlybecause timewiththehusbandis shared,but
gynylowersfertility
wifetendto have
marriedwomenbeyondthefirst
also becausepolygynously
marriedwomenand becausepolyeven olderhusbandsthanmonogamously
each have separatehouseholds,
gynouslymarriedwomennot infrequently
at greatdistancefromeach other.
sometimes
Polygynyis associatedwithtwo otherfactorsthataccountforlower
thanmonowives. First,theyare moreofteninfertile
of polygynous
fertility
marriedman will morefrequently
gamouswives, because a monogamously
takea secondwifeifhis firstwifeis childlessthanif she is not.This will be
thepracticeof
facilitates
discussedin greaterdetaillater.Second, polygyny
followingbirth,which
or abstinencefromintercourse
abstinence,
postpartum
of Africanfertility.
determinant
is a majorproximate
abstinenceOf the variouspossibletypesof sexual abstiPostpartum
abstinenceis themostnotableand widelypracticedform
nence,postpartum
in sub-SaharanAfrica.Wherelongperiodsof abstinenceare observed,their
whichis recognizedas
durationis generallytied to ongoingbreastfeeding,
of theinfant
and youngchild.
essentialto thehealthand normaldevelopment
throughout
extending
It is possiblethatatone timea periodofabstinence
inmostofAfrica.Thisis supported
beyond,was practiced
sometimes
lactation,
shortperiodstodaythatthepractice
fromgroupsobserving
reports
byfrequent
levelsdeclinesin theduration
was moreprolongedin thepast.Fromwhatever
of abstinencehave occurred,considerablevariationin the practicecan be
on abstinencein thelast
Africafrominformation
recognizedin contemporary
by ethnicgroup,the
20 or 30 years.However,whenmappedgeographically
durationsdisplaya highlevel of consistency.Such a mappinghas
different
et al. (1981), who dividethevariously
been carriedout by Schoenmaeckers
reporteddurationsfor sub-SaharanAfricaintothreegroups:durationsnot
IslamicizedgroupsfollowingKoranicpreexceeding40 days, to distinguish
durationsexceeding40 days and up to one year; and durations
scriptions;
by othersources,themappingof abstiexceedingone year.Complemented
(see Figure5).
revealsfairlydistinctpatterns
nencedurations
of40 daysorlessclusterinthelakeregionsofeastern
durations
Reported
centralAfricaand in scatteredpartsof the Sahel (amongsome Islamicized
Africa.Reported
durations
exceeding
groups)andofsoutheastern
westAfrican
east
ineasternAfrica(generally
40 daysandup to one yearclusterremarkably
ofthelakeregions),butoccuralso inwestAfrica(Ghana).Finally,postpartum
of two yearsor
abstinenceperiodsof greaterthanone year(and frequently
ofall reports,
arefoundthroughbyfarthelargestproportion
more),comprising
out sub-SahelianwestAfricaand centralAfrica.
on fertility
abstinence
dependscritThe potentialimpactof postpartum
In
icallyon itsdurationin relationto thedurationof lactationalamenorrhea.
of
on
exabstinence
duration
effect
of
the
postpartum
quantitative
assessing
theconceptofthenonsusceptible
period,which
posure,itis usefultointroduce
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John Bongaarts
/ Odile Frank
/ Ron Lesthaeghe
FIGURE 5 Durations of postpartum abstinence
Saharan Africa, broad geographic regions
523
among ethnic groups in sub-
[1 ?40 days
> 40 days-iyear
>1 year
WNo data
from
Schoenmaeckers
etal. (1981).
SOURCE:Adapted
ofabsenceofriskofconception,
whether
theprotection
equalsthetotalduration
is providedby lactationalamenorrhea
or by abstinence.But it is thenalso
theeffectsat thelevel of theindividualand
necessaryto analyzeseparately
of thepopulation.For individualwomen,thedurationof thenonsusceptible
ofabstinence
ortheduration
ofamenorrhea,
whichperiodequals theduration
ever is longer.On thepopulationlevel thereis substantial
variationaround
themeandurations
ofabstinence
andamenorrhea,
so thattheaverageduration
of thenonsusceptible
will
be
than
the
ofeither
averageduration
period
longer
abstinenceor amenorrhea
(Lesthaeghe,1984).
Sincebreastfeeding
insub-Saharan
Africatendstobe practiced
farlonger
thana yearin themajority
of ruraland traditional
societies,it is theeffectof
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524
Fertility Determinants
in sub-Saharan
Africa
relevanceto fertility.
of abstinencethathas thegreatest
thelongestdurations
exceeds
In fact,thereis ampleevidencethat,amonggroupswhereabstinence
and
of breastfeeding
tiedto theduration
is purposefully
one year,itsduration
lastsat leastuntilweaning(in some groups,suchas theYoruba
customarily
at all durations).As a result,in
of Nigeria,abstinenceexceedsbreastfeeding
womendo notbegin
extendedabstinence,
of societiespracticing
themajority
is weaned,which
recent
child
most
untilaftertheir
tobe exposedtoconception
can lead to a spacingbetweensuccessivechildrenof up to aroundfouryears.
of abstiof all durations
of thedistribution
close scrutiny
Nevertheless,
ofthemostrecent
examination
Africa,and,inparticular,
nencein sub-Saharan
is notonlyrelatedto differentials
surveys,revealquicklythatthisdistribution
theongoingerosionofthesepractices,
practices,butalso reflects
incustomary
The near
variesacrossthecontinent.
a processwhose stateof advancement
inTanzania,
oftheerosionprocessata nationallevelcanbe inferred
completion
butitsresultsare possiblybestobservedin Kenya.In Tanzaniain the 1970s,
durations
showvaryinglevelsandmixedpractices,butrarelyexceed
reported
Surveyof 1977-78 revealedan average
six months.In Kenya,theFertility
durationof abstinenceof aboutfourmonths.The declineof the abstinence
durationin Kenya can be presumedto have playeda role in the country's
increase,whichwill be examinedlater.Finally,oftenlarge
overallfertility
andbetweenthoseofeducational
betweenruralandurbanpractices
differentials
toward
othernationaltransitions
groupssuchas foundinrecentsurveysportend
suspected)
of thepractice,iftheyindeedindicate(as is strongly
abandonment
thefirststepin theprocess.
Spousal separationLong periodsof separationof spousescan appreare
ciablyreducewomen'soverallexposureto conception.Such separations
and are particularly
widespreadin
due to male labor migration,
principally
of considerable
is a phenomenon
imporsouthern
Africa.Laboroutmigration
of untancein westAfricaalso, buttendsto involvelongertermmigration
rather
thanto have
to havebolsteredpolygyny
marriedmenand consequently
is less
In southern
Africa,polygyny
in widespreadspousalseparation.
resulted
menwillbe absentforseveral
ofmigrating
married
common,andthemajority
reducetheoverallfremonthsor even a few years,whichcould drastically
in a marriedlifetime.
quencyof intercourse
inexposuretimecan be strongly
ofthisreduction
The impacton fertility
that
bythetimingof spousalseparation.In someareasit is reported
tempered
andintendtheirperiodofabsence
husbandsleaveoncetheirwivesarepregnant
long
and thechild's earlylife. Unexpectedly
to coincidewiththepregnancy
Survey
durations
ofpostpartum
abstinence
werefoundin theLesothoFertility
thistimingeffecton a nationalscale. Because of
of 1977, thusillustrating
of males to the Republicof South Africa,the
large-scalelabor migration
in all probability
measuresthecustomary
absence
longabstinence
surprisingly
betweencohabiting
thanabstinence
ofhusbandsinthepostpartum
period,rather
spousesperse.
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John Bongaarts
Breastfeeding
/ Odile Frank
/ Ron Lesthaeghe
and lactational
525
amenorrhea
blocksovulationfor
Becausethebiologicalfeedbackfromsucklingeffectively
have a potentially
of breastfeeding
a periodof time,thelengthand intensity
on theperiodof timethata womanis exposedto conception.
largeinfluence
The lengthof timeduringwhichovulationis blockedby lactation(lactationalamenorrhea)falls shortof the totaldurationof lactation,because
of sucklingdeclineas weaningapproaches,butlacfrequency
and intensity
of theperiodof breastfeeding
lastsfora majorproportion
tationalamenorrhea
The relationship
betweentheaveragedurations
durations.
at all breastfeeding
by Bongaartsand Potter.
of amenorrhea
and lactationhas been quantified
lasts
Accordingto theiranalysisof a largenumberof data sets,amenorrhea
forabouttwomonthsfollowingdeliveryin theabsenceof anylactation.The
to the lengthof
increasesin proportion
durationof lactationalamenorrhea
ofbreastfeeding
oftheduration
lastingforabout60 to70 percent
breastfeeding,
durationsare up to one to two yearsand more.For the
wherebreastfeeding
amenorrheic
periodsof up to twoyearsoccur
durations,
longestbreastfeeding
(Bongaartsand Potter,1983).
subis universalthroughout
and purposes,breastfeeding
For all intents
initsduration
betweencountries,
variation
SaharanAfrica.Thereis substantial
in practiceto a largeextent,and the
ethnicdifferences
however,reflecting
to a measurableextent.
negativeeffectsof modeminfluences
is about19 monthsin Lesotho,18
The meandurationof breastfeeding
monthsin Ghana,and about 16.5 monthsin Sudan and Kenya.The average
are
forthesebreastfeeding
durations
periodsdue to amenorrhea
nonsusceptible
about 13 monthsin Lesotho, 12 monthsin Ghana,and 11 monthsin Sudan
of theaverageduration
and Kenya.However,theseare theminimalestimates
arenotincluded(see thediscussion
effects
sinceabstinence
ofnonsusceptibility
theadded effectof abstinencepracticewouldraisethe
above). To illustrate,
meannonsusceptible
periodto 18 monthsin Lesotho,17 monthsin Ghana,
12 monthsin Sudan,and 13 monthsin Kenya(Casterlineet al., 1983).
Use of birth control
Birthcontrolthatis intendedto limitfamilysize includesboththe use of
and thepracticeof inducedabortion.
contraception
stillplaysa verylimitedrole in determining
The use of contraception
in sub-SaharanAfrica.On theone hand,knowledgelevels are very
fertility
low: theproportion
of ever-married
womenwhoreportneverhavingheardof
rangesfrom12 percentin Kenya,
any methodto delayor avoid a pregnancy
32 percentin Ghana, 35 percentin Lesotho,40 percentin Senegal,and 49
percentin Sudan to 66 percentin Cameroon.On theotherhand,even better
use
associatedwithhigheruse: current
levelsofknowledgearenotnecessarily
andsterilization)
ofanymethodofcontraception
traditional
methods
(including
marriedwomenrangesfromabout9.5 percentin Ghana
amongall currently
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526
Fertility Determinants
in sub-Saharan
Africa
to 5-6 percentin Kenya,Nigeria,Sudan,and Lesotho,and below 5 percent
in Senegal. Taking accountonly of womenwho are currently
exposed to
are higher-12.4 percentin Ghana,9.2 percent
conception,theproportions
in Kenya,7 percentin Lesotho,6 percentin Sudan and in Nigeria,and 5.2
in Senegal-but a thirdormoreoftherespondents
percent
areusinginefficient
methods(in Senegal,themajority).
Data on inducedabortionare veryrarein sub-Saharan
Africa.Overall,
abortionis probablyused in a number
ofurbanareasamongtheveryyoungest
womenbeforemarriage,butotherwise
thepracticeappearsto be infrequent.
Theurbanphenomenon
is reported
variously
torepresent
an increasing
problem
of publichealth,but at theregionallevel inducedabortionhas a negligible
effecton fertility
levels.
Fetal loss
Intrauterine
mortality
includesbothspontaneousabortions,whichcomprise
thebulkof pregnancy
afterthe28thweekof
losses, and stillbirths
(mortality
pregnancy).
is
Thereare good reasonsto believethatoverallintrauterine
mortality
similarin all humanpopulations-probably
around20 percent(Bongaartsand
in Africathan
while theymay be morefrequent
Potter,1983). Stillbirths,
of intrauterine
so smalla proportion
as to have
elsewhere,constitute
mortality
a negligibleeffecton thetotal.
Thereis evidencethatepidemicmalariamaybe associatedwithhigher
and sincemalariais widespreadin Africa,it
levelsof intrauterine
mortality,
could affecttheoveralllevels of intrauterine
mortality.
However,malariais
is stable,whichmay
highlyendemicin muchof Africa,and itstransmission
resultin a loweroveralleffecton fetalloss in contrast
to regionswhereit is
to
the
absence
of
data
make
a
better
epidemic.Notwithstanding
determination,
is deemednegligiblerelativeto theorderof magnitude
theeffecton fertility
of expectedlevelsof fetalloss (Lancet,1983).
Sterility
arisesfrombothnaturaland pathologicalcauses. In thisdiscussion
Sterility
theprevalence
ofsterility
is measured
thatis,thelevelofinfertility.
byitsresult,
ofreproductive
lifein
Naturalinfertility
The naturalmaximum
duration
womenis frommenarcheto menopause.Bothtermsdenotea processrather
is followedby a
thana well-defined
event.The onsetof firstmenstruation
or otherwiseincomplete
periodduringwhichanovulatory
cyclesoccurwith
so thatpopulationsof womenexperiencea periodof
decreasingfrequency
fora numberof yearsin the earliest
naturally
occurringrelativeinfertility
portionof thereproductive
span,theactualyearsof age involveddepending
on theage at menarche.Averageage at menarche
has beenfoundto rangein
the 1960s and 1970s fromabout 12 to 19 yearsforvariouspopulationsfor
whichthereare relevantdata. ExistingdataforAfricarangenearlyas widely
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John Bongaarts
/ Odile Frank
/ Ron Lesthaeghe
527
or urbangroups
in thesame timeperiod:fromabout 13 yearsamongaffluent
in Ugandaand Nigeriato over 17 amongruralHutiin Rwanda.Averageage
at menarcheevidentlydependson a numberof bothgeneticand nutritional
factors,althoughtheroleof anyone factoris notwell known(Gray,1979).
lifeofwomenis relatively
oftheearlyreproductive
The naturalinfertility
of thelateryears,since
thanthenaturalinfertility
less important
to fertility
is lostthrough
andbecauselateage atmenarche
nonexposure
muchofitseffect
tendsto be associatedwithlaterage at marriage.
Menopauseis the finalpointin a processof severalyears' duration
declineuntilovulation
ceases.
andregularity
ofovulation
thefrequency
whereby
Evidencefroma numberof studiessuggeststhatin a populationof women
theprocessbeginsin the30s, halfof thewomenare menopausalat theend
of their40s, and all womenare menopausalby themiddleto end of the50s.
precedesmenopauseby a
However,it is clear thatthe onsetof infertility
numberof years.This is becausein additionto irregular
and infrequent,
even
systemis associatedwitha higher
rare,ovulation,agingof thereproductive
frequency
of earlyspontaneousabortions,and olderwomentendto have a
ofintercourse.
therefore,
theprocesstransMostimportantly,
lowerfrequency
lates into a mean age at last birthof about 40 in populationsthatdo not
at an earlierage (Bongaartsand Potter,1983).
intentionally
stopchildbearing
of onsetof menopauseis derivedfromotherpopthispattern
Although
Africa.The resulting
ofnatural
pattern
ulations,itis applicableto sub-Saharan
withage providesus witha lowerboundforprobablelevels of
infertility
in Africa.
thatis essentialto theanalysisof pathologicalinfertility
infertility
is at itslowestlevel,3 percentin the
Thus,theage at whichnaturalinfertility
of womenwe wouldexpect
early20s, providesus withthelowestproportion
all womenare exposedto
to be childlessforlifein a societywherevirtually
is confirmed
in thoseyears.This standard
levelofchildlessness
by
conception
of ever-married
womenendingtheirreproductive
thelowestproportion
years
childless(around3 percent)in a numberof populations.
occasionsbothpriThe prevalenceof gonorrhea
Pathologicalinfertility
Africa.For any
in manypartsof sub-Saharan
maryand secondaryinfertility
is
an
there
or
of
accompanying
larger
level primary
infertility childlessness,
women
these
of womenwho have incurredsecondaryinfertility:
proportion
are unableto have additionalchildren,sometimesveryearlyin theirchildof womenchildlessaftertheend of childbearing
bearinglife.The proportion
infertility,
weightofprimary
(say,ages 45-49) allowsus to gaugetheultimate
oftheextent
ofaccompanying
andtogaina goodindication
infertility
secondary
(see Frank,1983b).
The highestlevelsof infertility
(20 percentor moreof womenaged 4549 childless)are foundacross a largearea of centralAfrica.Lower levels
ofwomen45-49 childless)arefoundininterspersed
(between12and20 percent
areas of centralAfricaand in east Africa.In generalmuchlowerlevels,but
(3 to 12 percent
ofwomen45-49 childless),
stillexceedingexpectedinfertility
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Fertility Determinants
528
in sub-Saharan
Africa
is foundamonga
are foundacross west Africa,althoughhigherinfertility
numberof Saheliangroupsof upperwestAfricaand in some coastalareas.
yearsand
at theendofthereproductive
betweenchildlessness
The relationship
accountsfor
in 18 sub-Saharancountriesshowsthatinfertility
totalfertility
point
and thateach 9 percentage
about60 percentof variationin totalfertility
into
of women45-49 whoarechildlesstranslates
in theproportion
increment
a dropin totalfertility
of one live birth.Childlessnessamongwomenin 21
Africaforwhichdataare availableaverages12 percountries
of sub-Saharan
of 3 percent,women
naturalinfertility
cent:thismeansthat,afterdiscounting
of one live birthdue to pathoin thesecountries
have on averagea shortfall
(Frank,1983a).
logicalinfertility
Summary and prospects
of fertility
ofthelevelsanddifferentials
determinants
The principal
proximate
dedue to breastfeeding,
in sub-SaharanAfricaare lactationalamenorrhea
andpathosexualabstinence,
duetopostpartum
creasedexposuretoconception
due to gonorrhea
(Frank,1983b).
infertility
logical,involuntary
determinants
dependon behaviorsthatare susThese threeproximate
ceptibleto moderninfluencesin Africa,especiallythoseof educationand
later,
theytendtomarry
urbanization.
Thus,educated,urbanwomen,although
abstainsexuallyforshorter
periodsafterdeliveryandtendto replace
generally
milkorsolidfoods.Recourse
withalternative
earlieroraltogether
breastfeeding
couldcompensateforthepositiveeffectsthesechangeshave
to contraception
is clearlylagging.In Kenya,for
on fertility,
butacceptanceof contraception
urban
is ineffect
amongyoung,educated,married
increasing
example,fertility
hasbeenobservedinseveralstudiesinNigeria,
women.The samephenomenon
is higheramong
thatcurrent
fertility
andtheNigeriaFertility
Surveyconfirms
educationcomparedto womenwithless or none,and
womenwithprimary
amongwomenwithan urbanresidence(FederalRepublicof Nigeria,1983).
Broadextension
ofeducationforwomenin ruralareascouldbringaboutthese
effectsat nationallevels, but some erosionof abstinenceand breastfeeding
increases
can be expectedto occurevenin theabsenceofsubstantial
durations
in women'seducation.
in verydifferent
andeducationmayaffectinfertility
Urbanization
ways.
of healthinfrastructure
withoutconcomitant
development
Rapid urbanization
because the incidenceof gonorrheais incould fosterincreasedinfertility,
sexualmobility,
creasedbythegreater
exogamy,and incidenceofprostitution
areas. On the otherhand, the meregreateravailabilityof
in metropolitan
areaswitheven
in somerapidlyurbanizing
could reduceinfertility
antibiotics
Womenwithlowlevelsofeducationgenerally
highlyinadequateinfrastructure.
thanwomenwithno educationat all, whichmay
havehigherlevelsof fertility
Whilehigherlevelsof educationbeginto
be in partdue to lowerinfertility.
onfertility
showvariousothereffects
perse canbe expected
behavior,infertility
as womenhave increasedaccess to health
to declinefairlysystematically
use oftheseresourceswiththeirincreased
resources,and makemoreeffective
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John Bongaarts
/ Odile Frank
/ Ron Lesthaeghe
529
pathexperiencing
ofruralpopulations
educationalexposure.Forthemajority
at a
only
occurring
are
probably
changes
these
however,
infertility,
ological
slow rate.
Fertility and the proximate
determinants
Estimating the fertility-inhibiting effects
of the proximate determinants
determinants
oftheproximate
theeffect
A convenient
approachto quantifying
In otherwords,delayedentrance
of fertility.
is to considerthemas inhibitors
abpostpartum
breastfeeding,
intothefirstsexual union,maritaldisruption,
to levelsbelowthose
thatreducefertility
areall factors
andinfertility
stinence,
variables.
thatwouldprevailin theabsenceof theeffectsof theseproximate
can be substantial.
performance
Theirconsequencesforoverallreproductive
may resultin a periodof lactational
For example,prolongedbreastfeeding
of three
of 18 months.In a populationwitha meanbirthinterval
amenorrhea
birth
interval
and
hence
that
half
the
for
this
means
unusual
Africa),
(not
years
within
could
be
amenorrheic
women
spent
halfthemarriedlifeof nonsterile
but
in thisexampleis clearlyimportant,
periods.The impactof breastfeeding
variables,
effectsof otherproximate
in orderto compareit withthefertility
the relationship
model thatquantifies
it is necessaryto use a mathematical
of the
A detaileddescription
and itsproximate
determinants.
betweenfertility
modelused herecan be foundin Bongaartsand Potter(1983). This model
variableintoitsproportional
a measureof each proximate
basicallytranslates
rate.4
as measuredin thetotalfertility
effecton fertility
an applicationof thismodel,we use thefollowingfairly
To illustrate
in sub-Saharan
Africa:
determinants
typicalvaluesfortheprincipalproximate
-
of reproductive
yearsnotlivingin union(weightedaverage):
Proportion
0.15
-
amongwomenin union:0.05
contraception
practicing
Proportion
Durationof postpartum
period:16 months
nonsusceptible
childlessat end of thereproductive
years:0.10 (an indicator
Proportion
of theincidenceof pathologicalsterility)
Fromthesemeasuresthe model can estimatethe percentincreasein
effectofeach oftheseproxthatwouldoccurifthefertility-inhibiting
fertility
imatevariableswereremoved.The results,plottedin Figure6, indicatethat
abstinencewouldproducea
and postpartum
of breastfeeding
theelimination
The effectsof the othervariablesare much
rise of 72 percentin fertility.
smaller:18 percentfortimespentoutsideunions,12 percentforpathological
and 5 percentforcontraception.
Expressedin birthsperwoman,the
sterility,
rateof 6.6 would increaseto 11.4 without
averageobservedtotalfertility
and postpartum
effectsof nonabstinence;and if theinhibiting
breastfeeding
were also
exposure to unions, pathologicalsterility,and contraception
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530
Fertility
Determinants
in sub-Saharan
Africa
would reachover 15 birthsper woman. Obviously,the
removed,fertility
period,have a
proximate
variables,especiallythepostpartum
nonsusceptible
in sub-Saharan
Africa.
powerful
negativeeffecton fertility
in fertility associated
FIGURE
6
Estimated
percent increase
effect of various
with removal
of fertility-inhibiting
proximate
variables,
by continent
ASSOCIATED
RISE IN FERTILItY
WrEN
REtMOALOF:
RASTFEEDINGAND
ABSTINENCE
POSTPARTUM
TIME OUrSDE
MARRL'GE
ORUNIONS
CONTRACE'TON
PATHOLOCICAL
STEIRIlITY
0
50
25
75
Percentincreasein fertility
SUB-SAHARA
ARIA
-
AS
LATINAMERNCA
SOURCES: For sub-Saharan
Africa,see text;forAsia and LatinAmerica,
Casterlineet al. (1983).
effectsof the
Figure6 also containsestimatesof thefertility-inhibiting
variablesfromsetsofAsianandLatinAmericancountries.
A comproximate
Africaindicatesthattheeffectsof
parisonwiththeestimatesforsub-Saharan
greaterin
marriageor unionexposureand of contraception
are considerably
LatinAmericaandAsia. On theotherhand,insub-Saharan
Africathefertilityeffectsof postpartum
and of pathologicalsterility
inhibiting
nonsusceptibility
exceedthoseobservedelsewhere.
substantially
Differentials
proximate
in fertility and the
variables
thevariationsin fertility
amongregionsand
By definition,
amongcountries,
and amongindividualwomenare due
socioeconomicstratawithincountries,
variables.If accuratemeasures
to theeffects
of one or moreof theproximate
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John Bongaarts
/ Odile Frank
/ Ron Lesthaeghe
531
of all proximatevariablesas well as a completemodel were available,all
measuresof some
could be explained.Unfortunately,
variancein fertility
As a consequence,itis not
variablesare unavailableor incomplete.
proximate
explanationof the
possible here to providea detailedand comprehensive
Inin fertility.
and individualvariations
sourcesof thenational,subnational,
theprincipalcauses of some
stead,a fewexampleswill be givento illustrate
fertility
differentials.
ratesof countries
As notedearlier,totalfertility
Nationaldifferentials
Africarangefrom8.1 in Kenyato 4.1 in Gabon. Two crucial
in sub-Saharan
were
betweenthesetwocountries
clues as to thecause of thegap in fertility
determinants:
Kenyahas
providedin theearlierdiscussionof theproximate
of thepostpartum
nonsusceptible
periodfoundin
durations
one oftheshortest
whichis
of
levels
has
childlessness,
Africa
and
Gabon
very
high
sub-Saharan
to what
To determine
of a highprevalenceof pathologicalsterility.
indicative
in fertility
between
extentthesetwo factorscan accountforthe difference
Kenyaand Gabon,a simpletwo-stepcalculationis madewiththemodelused
intheprevioussection.First,an estimateis madeofthedeclineintotalfertility
fromits
periodwerelengthened
thatwouldoccurif Kenya's nonsusceptible
toa moretypical16months.
Second,theincrease
of 13 months
current
duration
is estiof pathologicalsterility
in Gabon's fertility
followingtheelimination
period
mated.The resultsareplottedinFigure7. The riseinthenonsusceptible
ratefrom8.1 to 7.4, whileGabon's total
in Kenyareducesits totalfertility
forthehigherprevalenceof
raterisesfrom4. 1 to 7.3 aftercorrecting
fertility
between
difference
havecutthefertility
Thesesimpleadjustments
childlessness.
there
KenyaandGabonfrom4 to a negligible0. 1 birthsperwoman.Although
betweenthese
in otherproximatedeterminants
differences
are undoubtedly
shortduration
of
it appearssafeto concludethattherelatively
twocountries,
the nonsusceptible
periodin Kenya and the highincidenceof pathological
determinants
of thelargegap in
in Gabonare theprincipalproximate
sterility
ratesbetweenthesetwocountries.
observedtotalfertility
To carryout a similarexerciseon thesubnaSubnationaldifferentials
tionallevel requiresmoredetailedmeasuresof the proximatedeterminants
aboutthedifferentials
thanare currently
available,buta fewgeneralizations
plottedearlierin Figure2 can be made:
in Cameroonare largelycaused by varia(1) The regionaldifferences
tionin levels of childlessness,whichranged(in the 1960s) from29 percent
of
in theSoutheastto 7 percentin theWest(Frank,1983b). The elimination
would, accordingto the model,raise the totalfertility
pathologicalsterility
ratefrom4.3 to 7.1 in theSoutheastand from6.5 to 6.9 in theWest.Thus,
levels in these
fertility
afteradjustingfortheeffectof pathologicalsterility,
equal.
tworegionsof Cameroonare virtually
ratesamongbettereducatedand urbanwomen
(2) The lowerfertility
caused by laterage at firstunionand by higherprevalenceof
are primarily
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532
Fertility Determinants
FIGURE 7 Observed
Gabon, 1975-80
and adjusteda
in sub-Saharan
Africa
fertility rates in Kenya and
OBSERVED FERTILITY
KENYA
GABON
ADJUSTED FERTILITY
KENYA WITH 16-MONTH POSTPARTUM
NONSUSCEPIIBLE PERIOD
GABON WITHOUT PATHOLOGICAL
0
5
10
Total fertility
rate
effectsof the
are based on modelestimatesof thefertility-inhibiting
Adjustments
postpartum
nonsusceptible
periodand pathologicalsterility
a
SOURCE: UnitedNations(1982) and text.
contraceptive
practice.However,higherlevels of educationand urbanresidenceare also associatedwithshorter
durations
of postpartum
abstinence
and
andperhapswithlowerlevelsofpathological
breastfeeding
Thistends
sterility.
to offsetthefertility-inhibiting
effectsof latermarriageand greaterextentof
contraceptive
practice.In fact,thisoffsetting
effect
can be so largeas to result
in a risein fertility
withincreasing
educationin some strata.This is themost
likelyexplanationforthe higherfertility
amongwomenwith 1-3 yearsof
schoolingthanamongwomenwithno schooling(see Figure2).
As on the nationaland subnationallevels, the
Individualdifferences
proximate
determinants
areresponsible
fortheverylargevariations
inchildren
everbornamongindividualwomen.The simplefertility
modelused thusfar
on the aggregatelevel is inadequateto accountforindividualdifferences.
Instead,an analysiswithhighlycomplexcomputer
simulation
modelswould
be requiredto studythistopicin detail,a taskthatfallsoutsidethescope of
thispaper(see Bongaartsand Potter,1983, forapplications
of suchmodels).
A fewrelevant
observations
canbe made,however.In general,bothbehavioral
and biologicalfactorsare involvedin determining
thenumberof childrena
womanwill have. Behavioralvariablesincludetheage at first
union,theuse
of contraception,
thepattern
and duration
of breastfeeding,
and thefrequency
ofintercourse.
Thesebehavioral
factors
accountforsomeoftheindividual
variationin fertility,
in behavior,thenumberof
butin theabsenceof differences
childreneverbornwouldstillrangefromzero to overten.This pointsto the
crucialroleplayedby biologicalfactorsat theindividuallevel. For example,
naturalsterility,
whichat theaggregatelevel has littleexplanatory
power,is
a majorcause of variation
becausea womanwhois sterile
amongindividuals,
whenshe entersher firstunionwill remainchildless,while a womanwho
remainsfertileuntilage 50 will have severaldecades of reproductive
life,
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John Bongaarts
/ Odile Frank
/ Ron Lesthaeghe
533
whichis sufficient
to producetenor even 15 births.In addition,thespacing
betweenbirthsrangesfromabouta yearto severalyearsevenamongwomen
withthe same breastfeeding
and intercourse
patterns,
because durationsof
lactationalamenorrhea,
occurrencesof spontaneousabortions,and waiting
timesto conception
areto a largeextentrandomly
determined.
The roleplayed
bychanceis one ofthemostimportant
causesofthelargerangeinthenumber
of childreneverbornamongindividualwomenat theend of thereproductive
years.
Implications
in fertility
for future trends
The precedinganalysisconstitutes
a basis fromwhichsome implications
for
future
fertility
trendscan be derived.Naturally,
anydiscussionof thedemographicfuture
of sub-Saharan
Africahas to be in largepartspeculativedue to
theabsenceof reliablemeasuresof current
and pasttrendsin fertility
and the
The factthattheoutlookforeconomicdevelopment
proximate
determinants.
is veryunclearaddsfurther
butwe willassumehereforsimplicity
uncertainty,
thatsub-SaharanAfricawill (slowly)followthegeneralpattern
of modernizationand development
foundelsewherein theworld.
Futuretrendsin fertility
are entirely
determined
by trendsin theproximatedeterminants.
The proximate
determinants
can be dividedintotwogeneral classes: thosethatcan be expectedto exertupwardpressureon fertility
in thefuture
and thosethatwill tendto reducefertility:
-
and postpartum
of breastfeeding
trends:shortening
Fertility-enhancing
abstinence;declinein pathologicalsterility
trends:risein age at first
Fertility-reducing
union;higherprevalenceand
effectiveness
of contraception
theoveralltrend
Thesearethemainvariablesthatarelikelytodetermine
even thoughsome otherproximatedeterminants
in fertility
(e.g., induced
roleinsomesocieties
ofintercourse)
abortion,
frequency
mayplaya significant
will rise or fall in the nearfuturetherefore
or subgroups.Whetherfertility
and fertility-reducing
trends
dependson thebalanceof thefertility-enhancing
in theproximate
determinants.
insub-Saharan
indication
Pastfertility
trends
Africaprovidean important
of whatmightlie ahead. Althoughmostcountrieshave not experienceda
in recentdecades,thereis one important
significant
changein fertility
excepratein Kenyahas
tion:Kenya. Accordingto UN estimates,thetotalfertility
risenfrom6.6 in 1950-55 to 8. 1 in 1975-80. Althoughit is possiblethatthe
estimatefortheearlierperiodis notentirely
accurate,therecan be littledoubt
This increaseoccurreddespitea rise
thatfertility
has increasedsignificantly.
inage at marriage
becausethepostpartum
nonsusceptible
periodwas shortened
andpostpartum
due to reductions
in traditionally
longperiodsofbreastfeeding
is boundeventually
to declinebelow itspresent
abstinence.Kenya's fertility
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534
Fertility Determinants
in sub-Saharan
Africa
veryhighlevel,butif itspastexperienceis anyguideto whatlies ahead for
othercountries,
thena risein fertility
in manycountries
of sub-Saharan
Africa
maybe inevitable.This is especiallytruein countries
wherethedurations
of
andpostpartum
are stilllongor wheretheprevalence
breastfeeding
abstinence
of pathologicalsterility
is high.Moreover,themerepresenceof infertility
in
a societywill impedethe acceptanceof contraception,
because the riskof
whichin turntendsto weaken
becomingsterilemakeschildbearing
uncertain,
in controlling
individuals'interest
theirfertility.
is foundincross-sectional
Supportfora possibleupwardtrendinfertility
studiesthatcorrelate
socioeconomic
indicators
ofregionswithlevelsoffertility
andtheproximate
variables.Forexample,Lesthaeghehas collectedestimates
of threeproximate
variables(maritalexposure,contraception,
andpostpartum
fora largeset of regionsforwhicha measureof literacy
nonsusceptibility)
was also available.As expected,maritalexposureand duration
of postpartum
werelowestandtheprevalenceofcontraception
nonsusceptibility
was highest
in regionswiththehighestlevels of literacy.Usinga modelto estimatethe
in theleastliterateregionswas found
fertility
effectof thesetrends,fertility
to be less thanthatof regionswithhigherdegreesof literacyformostof the
observedrange.Onlyafterliteracyreachedlevelsabove70 percentof women
ofreproductive
declineas theeffect
ofincreasing
age didfertility
contraception
and laterage at firstunionoutweighed
theeffectof shorter
and
breastfeeding
abstinence(Lesthaeghe,1984). Although,as Lesthaeghenotes,
postpartum
onecannotsimplyuse suchcross-sectional
overtime,
analysistopredicttrends
thatthereis a potentialfora significant
thisfinding
confirms
rise in fertility
in sub-Saharan
Africa.
Anotherdemonstration
of the formidable
bechangesin reproductive
haviorthatwill be requiredto achievedeclinesin fertility
can be madewith
a modelthatprojectsfuturefertility
levels fromtrendsin theproximate
deTo simplify
thisexercise,we will examinetheeffecton marital
terminants.
of twoproximate
crucialto thereduction
offertility,
determinants
the
fertility
Table
postpartum
nonsusceptible
periodand theprevalenceof contraception.
3 providesan illustration
of two projectionsof the levels of contraceptive
in fertility
prevalencerequiredto reachspecifiedreductions
bytheyear2000.
Inthefirst
itis assumedthatcurrent
projection,
contraceptive
prevalence
among
marriedwomenof reproductive
age is 5 percentand thatthedurationof the
nonsusceptible
periodis 16 months.The secondcolumnof Table 3 provides
estimatesof thecontraceptive
prevalencelevelsneededto reducemaritalfertilityby 10, 20, and 30 percentrespectively,
assumingno changein breastabstinence.For example,a 20 percentreductionwill
feedingor postpartum
requirea contraceptive
prevalenceof 26 percentin theyear2000. The last
columnof Table 3 givestherequiredlevelsof contraceptive
prevalenceifthe
of thenonsusceptible
to
duration
were
reduced
months
period
eight
(thismay
well happenin substantial
partsof Africaby theyear2000). In thissecond
projection,contraceptive
prevalencewill have to rise to 29 percentjust to
an increaseinmarital
A modest20 percent
inmarital
reduction
prevent
fertility.
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John Bongaarts
/ Odile Frank
/ Ron Lesthaeghe
535
TABLE 3 Model estimates of levels of
contraceptive prevalence required to
achieve specified reductions in marital
fertility by the year 2000, for two
durations of the nonsusceptible
period
(NSP)
prevalencein
Percentreduction Requiredcontraceptive
2000
(percent)
in maritalfertility
by the year 2000
NSP= 16 months NSP= 8 months
0
10
20
30
5
15
26
36
29
37
45
53
will requirethatno fewerthan45 percentof marriedwomenengage
fertility
in contraception.
A dramatic
risein contraceptive
prevalenceis unlikelyto occurin most
of sub-SaharanAfricabeforetheend of thecentury.Desiredfamilysize is
higherin sub-Saharan
Africathananywhere
else in theworld,andthereis no
evidencethattraditional
normsare changing.Whatlittlecontrareproductive
ceptiveuse existsis foundpredominantly
amongolder,high-parity
women;
onlya verysmallproportion
of low-parity
womendeliberately
wantto stop
childbearing.
Large declinesin fertility
will notoccuruntilthesetraditional
of reproductive
patterns
behaviorare modified.It is worthnoting,however,
thatoverallfertility
could be reducedsignificantly
even if only high-parity
womenwereto stopchildbearing.
Thisis duetothefactthata largeproportion
of womenreachveryhighparitiesby theend of theirreproductive
years,as
is evidentfromFigure3. Eliminating
birthsof thehighestorderswouldbe a
first
steptowarda sustainedfertility
declinewhoseeffectcouldbe substantial.
For example,if Kenya were to adopt a stop-at-six
policy, this would, if
completelysuccessful,reducefertility
by 34 percent.Whilethisstillleaves
thetotalfertility
rateat 5.4, it wouldhave an important
effecton
moderating
therateof populationgrowth.
In sum,thereare no clearprospectsforan earlyand substantial
decline
of fertility
in sub-SaharanAfrica.Reductionsin fertility
will occuronly in
orstratawhereincreasesincontraceptive
populations
use andinage atmarriage
are sufficiently
largeto outpacetheeffectsof theshortening
of breastfeeding
and the abandonment
of postpartum
abstinenceas well as any declinesin
Urbanand well-educated
womenin themoredeveloped
pathologicalsterility.
Africancountriesare morelikelyto use contraception
or to delaymarriage,
andtheyaretherefore
also morelikelyto experiencefertility
declines.On the
otherhand,thelargemajority
of womenhave littleor no educationand live
inruralareas,andtheirprospects
forrapidincreaseincontraceptive
prevalence
are notgood, at leastin thenearfuture.Factorsthatare obstaclesto a rapid
behaviorarehighlevelsof illiteracy
andof infant
changein contraceptive
and
childmortality,
thelargenumbersof childrendesired,thehighprevalenceof
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536
Fertility Determinants
in sub-Saharan
Africa
pathologicalsterility
(in some societies),and thelack of access to healthand
familyplanningservices.
Notes
This analysiswas preparedas a background yses of World FertilitySurveysof African
paperfora WorldBank studyof population countriescarriedout by Lesthaeghe(1984).
forsub-Saharan
strategies
Africa.
The six countriesand the surveydates are
1 Sub-Saharan
Africais defined
heretoin- Cameroon (1978), Ghana (1979), Kenya
incontinental
cludeall countries
Africaexcept (1977-78), Lesotho(1977), Senegal (1979),
Egypt, Libya, Tunisia, Algeria, Morocco, and Sudan (1979). Full citationsare provided
in thereferences.
and theRepublicof SouthAfrica.
2 Since thepracticesof breastfeeding
and
4 The existingversionofthismodelquanpostpartum
abstinenceare usuallynota func- tifiesthe proportional
effertility-inhibiting
tionof achievedparityand are appliedwith fectsoffourproximate
variables:themarriage
minorvariationto all birthintervals,
theyare pattern,
inducedabortion,and
contraception,
consideredconsistentwith naturalfertility. postpartuminfecundability.
In the present
Naturalfertility
is definedbyHenryas fertility analysisa fifth
proximate
variable,pathologin theabsenceof deliberatebirthcontrolthat ical sterility,
is introduced.
Its effecton feris "bound to thenumberof childrenalready tilityis measuredwithan index,I, whichis
bornandis modified
whenthenumber
exceeds estimatedfromthe percentchildlessamong
themaximum
whichthecoupledoes notwish womenat theendofthereproductive
years(s)
to exceed" (Henry,1961).
using the equation I, = (7.63 - 0.11 x s)/
3 Unlessotherwisestatedthedata forsix 7.30. This equationis based on theresultsof
Africancountriesto whichreference
of thetotalfertility
is made a regression
rateon proin thefollowingdiscussionderivefromanal- portionchildlesspresented
by Frank(1983a).
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