The Reproductive Ecology of Industrial Societies, Part II : The Association between Wealth and Fertility.
Studies of the association between wealth and fertility in industrial populations have a rich history in the evolutionary literature, and they have been used to argue both for and against a behavioral ecological approach to explaining human variability. We consider that there are strong arguments in favor of measuring fertility (and proxies thereof) in industrial populations, not least because of the wide availability of large-scale secondary databases. Such data sources bring challenges as well as advantages, however. The purpose of this article is to illustrate these by examining the association between wealth and reproductive success in the United States, using the National Longitudinal Study of Youth 1979. We conduct a broad-based exploratory analysis of the relationship between wealth and fertility, employing both cross-sectional and longitudinal approaches, and multiple measures of both wealth (income and net worth) and fertility (lifetime reproductive success and transitions to first, second and third births). We highlight the kinds of decisions that have to be made regarding sample selection, along with the selection and construction of explanatory variables and control measures. Based on our analyses, we find a positive effect of both income and net worth on fertility for men, which is more pronounced for white men and for transitions to first and second births. Income tends to have a negative effect on fertility for women, while net worth is more likely to positively predict fertility. Different reproductive strategies among different groups within the same population highlight the complexity of the reproductive ecology of industrial societies. These results differ in a number of respects from other analyses using the same database. We suggest this reflects the impossibility of producing a definitive analysis, rather than a failure to identify the "correct" analytical strategy. Finally, we discuss how these findings inform us about (mal)adaptive decision-making.
Department of Population Health, London School of Hygiene & Tropical Medicine, Keppel Street, London, WC1E 7HT, UK.|Department of Sociology, University of Groningen / Inter-university Center for Social Science Theory and Methodology (ICS), Grote Rozenstraat 31, 9712, TG , Groningen, The Netherlands.
Gert
G
Stulp
Department of Population Health, London School of Hygiene & Tropical Medicine, Keppel Street, London, WC1E 7HT, UK. Rebecca.Sear@lshtm.ac.uk.
Rebecca
R
Sear
Department of Population Health, London School of Hygiene & Tropical Medicine, Keppel Street, London, WC1E 7HT, UK.
Susan B
SB
Schaffnit
Department of Sociology and Nuffield College, University of Oxford, Manor Road, Oxford, OX1 3UQ, UK.
Melinda C
MC
Mills
Department of Psychology, University of Lethbridge, Lethbridge, AB, T1K 3M4, Canada.
Louise
L
Barrett
D000328:Adult; D001723:Birth Rate / Q000208:ethnology; D003430:Cross-Sectional Studies; D019049:Developed Countries / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D007182:Income / Q000706:statistics & numerical data*; D008137:Longitudinal Studies; D008297:Male; D043762:Reproductive Behavior / Q000208:ethnology / Q000706:statistics & numerical data*; D014481:United States / Q000208:ethnology
Fertility; Income; NLSY79; Secondary database; Wealth
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