Predictable Parenthood

Kevin Lewis

March 31, 2024

New Evidence on the Motherhood Wage Penalty
Wei-hsin Yu & Janet Chen-Lan Kuo
Demography, forthcoming

U.S. women's age at first birth has increased substantially. Yet, little research has considered how this changing behavior may have affected the motherhood pay penalty, or the wage decrease with a child's arrival, experienced by the current generation. Using Rounds 1–19 of the National Longitudinal Survey of Youth 1997 (NLSY97), in this research note we examine shifts in hourly pay with childbirth for a cohort of women who became mothers mostly in the 2000s and 2010s. Results from fixed-effects models indicate that the motherhood pay penalty for NLSY97 women who had their first child before their late 20s is generally similar to that of previous cohorts. Those who became mothers near or after age 30, however, encounter a parenthood premium, as men do. The growing proportion of women delaying motherhood, coupled with the rising heterogeneity in motherhood wage outcomes by childbearing timing, contributes to a comparatively small motherhood penalty for this recent cohort. The pay advantage of “late mothers” cannot be explained by factors such as their labor market locations, number of children, stage of childrearing, marital status, or ethnoracial composition. Instead, the hourly gain stems from such mothers’ tendency to reduce working hours more than other mothers without experiencing a commensurate decrease in total pay. Unlike the fatherhood premium, the premium for late mothers does not lead to a real boost in income.

What's Behind the Dramatic Pre-2020 Declines in Hispanic/Latina Adolescent Childbearing? Decomposing Change by Age, Origin, and Nativity
Reanne Frank et al.
Journal of Adolescent Health, forthcoming

Methods: We use birth counts from the United States vital statistics system and population denominators from the United States decennial census long form 5-percent Public Use Microdata and the American Community Survey to conduct a decomposition analysis apportioning observed declines in Hispanic adolescent childbearing to: (1) compositional shifts in nativity, age, and region-of-origin and (2) subgroup changes in childbearing rates.

Results: The Hispanic adolescent fertility rate fell by over 71% from 2000 to 2019, with Mexican-Origin, United States-born, and younger adolescents exhibiting the steepest declines (79%, 70%, and 80% declines, respectively). Results from the decomposition analysis show that almost 90% of the decline is due to within-group rate change, with some variability by subgroup and by decade. Only 10% of the decline was due to compositional changes, with shifts in nativity driving much of the effect.

The impact of juvenile curfews on teenage birth rates
Aaron Gamino
Health Economics, forthcoming

I examine the effect of city-level juvenile curfews on teenage birth rates using the National Center for Health Statistics birth data from 1982 to 2002. I compare differences in birth rates between younger and older age groups in cities with and without curfew ordinances. Before curfew adoption, the age differential in birth rates trended similarly for cities that did and did not adopt a curfew. There were significant decreases in the age differential birth rates in cities that adopted a curfew relative to cities that did not. Curfews reduced birth rates by approximately 3 births per 1000 women ages 15–17. I find a decrease in birth rates among white women. The main results are corroborated using a variety of robustness checks and specifications.

Parental Labor Supply: Evidence from Minimum Wage Changes
Anna Godøy et al.
Journal of Human Resources, March 2024, Page 416-442

We analyze effects of the minimum wage on the labor supply of parents of young children. Distributional difference-in-differences and event-study models document a sharp rise in employment rates of single mothers with children ages zero to five following minimum wage increases. Effects are concentrated among jobs paying close to the minimum wage. We find corresponding drops in the probability of staying out of the labor force to care for family members. Results are consistent with simple labor supply models in which childcare costs create barriers to employment. Minimum wage increases then enable greater labor force participation and reduce child poverty.

How are they doing? The academic performance and mental wellbeing of world cup babies
Dirk Bethmann & Jae Il Cho
SSM - Population Health, March 2024

In June 2002, South Korea cohosted the 17th FIFA World Cup. Unexpected wins carried the Korean National Football Team to the semi-finals and sparked an unprecedented euphoria among Koreans. Die-hard fans and occasional football viewers, young and old, women and men flocked the streets side by side, cheered for their team, and partied through the nights. In the subsequent spring of 2003, the country experienced a temporary and significant increase in its fertility rate. Using a difference-in-differences design, we exploit the quasi-experimental nature of this episode to investigate the Beckerian trade-off between the quantity and quality of children born to parents in South Korea. Our results support the notion of an adverse effect on child quality. Students born approximately ten months after the World Cup tend to perform significantly worse in school. Moreover, our results uncover a hitherto overlooked aspect: the same students exhibit significantly higher degrees of mental wellbeing.

Pregnancy renders anatomical changes in hypothalamic substructures of the human brain that relate to aspects of maternal behavior
Klara Spalek et al.
Psychoneuroendocrinology, June 2024

Animal studies have shown that pregnancy is associated with neural adaptations that promote maternal care. The hypothalamus represents a central structure of the mammalian maternal brain and hormonal priming of specific hypothalamic nuclei plays a key role in the induction and expression of maternal behavior. In humans, we have previously demonstrated that becoming a mother involves changes in grey matter anatomy, primarily in association areas of the cerebral cortex. In the current study, we investigated whether pregnancy renders anatomical changes in the hypothalamus. Using an advanced delineation technique, five hypothalamic substructures were defined in longitudinal MRI scans of 107 women extracted from two prospective pre-conception cohort studies, including 50 women who were scanned before and after pregnancy and 57 nulliparous control women scanned at a similar time interval. We showed that becoming a mother is associated with volume reductions in the anterior-superior, superior tuberal and posterior hypothalamus. In addition, these structural changes related to hormonal levels during pregnancy and specific aspects of self-reported maternal behavior in late pregnancy, including maternal-fetal attachment and nesting behavior. These findings show that pregnancy leads to changes in hypothalamic anatomy and suggest that these contribute to the development of maternal behavior in humans, supporting the conservation of key aspects of maternal brain circuitry and their role in maternal behavior across species.

Sibling aggression is surprisingly common and sexually egalitarian
Amanda Kirsch et al.
Evolution and Human Behavior, March 2024, Pages 214-227

Two well-supported generalizations from aggression research are that: a) people are less likely to commit homicide against close kin compared to non-kin, and b) females are less likely to engage in direct aggression than are males. Aggression between siblings, however, is somewhat more complicated than one might surmise from those two generalizations. Data from 3 studies collected using undergraduate and Prolific samples (N = 1640) reveal classic sex differences in direct aggression between non-relatives, but not between sisters and brothers. Whereas only a small minority of females have hit a friend or an acquaintance, the majority of females, like the majority of males, have hit a sibling. Although reputational aggression is substantially less likely between siblings than between friends or acquaintances, mild forms of direct aggression (such as hitting) are quite frequent between siblings. Discussion considers several possible limitations of the findings reported here and considers results in light of Trivers' theory of parent-offspring conflict.


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