Children of the Future
The role of relative income in the share of children born out-of-wedlock in the USA
Georgios Mavropoulos & Theodore Panagiotidis
Empirical Economics, March 2023, Pages 1105-1120
This paper investigates the non-marital fertility evolution in the USA for the period between 1976 and 2016. Beyond the well-known determinants in this framework, we add and test for the Easterlin relative income hypothesis. Easterlin stresses the role of the material aspirations formed in childhood (denominator) relative to the current economic perspectives (numerator) of young men. That ratio defines the relative income. We employ panel dynamic techniques at the state level. We find a negative and statistically significant effect of the relative income in the share of children born out-of-wedlock. Most importantly, relative income is robust to the inclusion of marriage. The latter may imply a socio-economic mobility perspective.
Naming the Precious Child: New Evidence of Intentional Family Planning in Historical Populations
Joshua Goldstein & Guy Stecklov
Can the names parents gave their children give us insights into how parents in historical times planned their families? In this study, we explore whether the names given to the firstborn child can be used as indicators of family-size preferences and, if so, what this reveals about the emergence of intentional family planning over the course of the demographic transition. We analyze historical populations from 1850 to 1940 in the United States, where early fertility control and large sample sizes allow separate analyses of the White and Black populations. We also analyze Norway from 1800 to 1910, where there was a much later fertility transition. A split-sample method allows automated scoring of each name in terms of predicted family size. We find a strong relationship between naming and family size in the U.S. White population as early as 1850, for the Black population beginning in 1940, and for the Norwegian population in 1910. These results provide new evidence of the emergence of "conscious calculation" during the fertility transition. Our methods may also be applicable to modern high-fertility populations in the midst of fertility decline.
Method: We conducted a quantitative analysis of longitudinal data from the Panel Study of Income Dynamics (PSID). We utilized the multigenerational structure of the PSID and restricted-use geocodes to map kin proximity at every interview from 1981 to 2017. We cross-classified our sample by race and income, focusing on Black and White respondents across income quartiles (n = 171,501 person-periods).
Results: High-income White respondents showed the greatest increases in distance from kin over time, whereas proximity to kin among other race-income groups was relatively stable.
Genome-wide analysis identifies genetic effects on reproductive success and ongoing natural selection at the FADS locus
Iain Mathieson et al.
Nature Human Behaviour, forthcoming
Identifying genetic determinants of reproductive success may highlight mechanisms underlying fertility and identify alleles under present-day selection. Using data in 785,604 individuals of European ancestry, we identified 43 genomic loci associated with either number of children ever born (NEB) or childlessness. These loci span diverse aspects of reproductive biology, including puberty timing, age at first birth, sex hormone regulation, endometriosis and age at menopause. Missense variants in ARHGAP27 were associated with higher NEB but shorter reproductive lifespan, suggesting a trade-off at this locus between reproductive ageing and intensity. Other genes implicated by coding variants include PIK3IP1, ZFP82 and LRP4, and our results suggest a new role for the melanocortin 1 receptor (MC1R) in reproductive biology. As NEB is one component of evolutionary fitness, our identified associations indicate loci under present-day natural selection. Integration with data from historical selection scans highlighted an allele in the FADS1/2 gene locus that has been under selection for thousands of years and remains so today. Collectively, our findings demonstrate that a broad range of biological mechanisms contribute to reproductive success.
Generation of functional oocytes from male mice in vitro
Kenta Murakami et al.
Sex chromosome disorders severely compromise gametogenesis in both males and females. In oogenesis, the presence of an additional Y chromosome or the loss of an X chromosome disturbs the robust production of oocytes. Here we efficiently converted the XY chromosome set to XX without an additional Y chromosome in mouse pluripotent stem (PS) cells. In addition, this chromosomal alteration successfully eradicated trisomy 16, a model of Down's syndrome, in PS cells. Artificially produced euploid XX PS cells differentiated into mature oocytes in culture with similar efficiency to native XX PS cells. Using this method, we differentiated induced pluripotent stem cells from the tail of a sexually mature male mouse into fully potent oocytes, which gave rise to offspring after fertilization. This study provides insights that could ameliorate infertility caused by sex chromosome or autosomal disorders, and opens the possibility of bipaternal reproduction.