Procreation
Alex Kevern & Jeremy Freese
Northwestern University Working Paper, July 2014
Abstract:
Differential fertility is frequently overlooked as a meaningful force in longitudinal public opinion change. We examine the effect of fertility on abortion attitudes, a useful case study due to their strong correlation with family size and high parent-child correlation. We test the hypothesis that the comparatively high fertility of pro-life individuals has led to a more pro-life population using 34 years of GSS data (1977-2010). We find evidence that the abortion attitudes have lagged behind a liberalizing trend of other correlated attitudes, and consistent evidence that differential fertility between pro-life and pro-choice individuals has had a significant effect on this pattern. Future studies should account for differential fertility as a meaningful force of cohort replacement in studies of public opinion where parents and children are likely to share the same attitude.
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Intelligence and childlessness
Satoshi Kanazawa
Social Science Research, November 2014, Pages 157–170
Abstract:
Demographers debate why people have children in advanced industrial societies where children are net economic costs. From an evolutionary perspective, however, the important question is why some individuals choose not to have children. Recent theoretical developments in evolutionary psychology suggest that more intelligent individuals may be more likely to prefer to remain childless than less intelligent individuals. Analyses of the National Child Development Study show that more intelligent men and women express preference to remain childless early in their reproductive careers, but only more intelligent women (not more intelligent men) are more likely to remain childless by the end of their reproductive careers. Controlling for education and earnings does not at all attenuate the association between childhood general intelligence and lifetime childlessness among women. One-standard-deviation increase in childhood general intelligence (15 IQ points) decreases women’s odds of parenthood by 21-25%. Because women have a greater impact on the average intelligence of future generations, the dysgenic fertility among women is predicted to lead to a decline in the average intelligence of the population in advanced industrial nations.
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Shuyang Yao et al.
Evolution and Human Behavior, forthcoming
Abstract:
Criminality is highly costly to victims and their relatives, but often also to offenders. From an evolutionary viewpoint, criminal behavior may persist despite adverse consequences by providing offenders with fitness benefits as part of a successful alternative mating strategy. Specifically, criminal behavior may have evolved as a reproductive strategy based on low parental investment reflected in low commitment in reproductive relationships. We linked data from nationwide total population registers in Sweden to test if criminality is associated with reproductive success. Further, we used several different measures related to monogamy to determine the relation between criminal behavior and alternative mating tactics. Convicted criminal offenders had more children than individuals never convicted of a criminal offense. Criminal offenders also had more reproductive partners, were less often married, more likely to get remarried if ever married, and had more often contracted a sexually transmitted disease than non-offenders. Importantly, the increased reproductive success of criminals was explained by a fertility increase from having children with several different partners. We conclude that criminality appears to be adaptive in a contemporary industrialized country, and that this association can be explained by antisocial behavior being part of an adaptive alternative reproductive strategy.
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Changing Fertility Regimes and the Transition to Adulthood: Evidence from a Recent Cohort
Andrew Cherlin, Elizabeth Talbert & Suzumi Yasutake
Johns Hopkins University Working Paper, June 2014
Abstract:
Recent demographic trends have produced a distinctive fertility regime among young women and men in their teenage years and their twenties -- a period sometimes called early adulthood. Data from the National Longitudinal Survey of Youth, 1997 cohort, show that by the time the cohort had reached ages 26-31 in 2011, 81% of births reported by women and 87% of births reported by men had occurred to non-college graduates. In addition, 57% of births had occurred outside of marriage for both men and women. Moreover, 64% of women (and 63% of men) who reported a birth had at least one child outside of marriage, a figure that rose to 74% among women (and 70% among men) without 4-year college degrees. It is now unusual for non-college-graduates who have children in their teens and twenties to have all of them within marriage. The implications of these developments are discussed in light of the differing transitions to adulthood of non-college-graduates versus college-graduates and the growing social class inequalities in family patterns.
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Red Alert: Prenatal Stress and Plans to Close Military Bases
Kyle Carlson
Caltech Working Paper, June 2014
Abstract:
In May 2005 the U.S. military announced a restructuring plan called Base Realignment and Closure (BRAC). Some areas were projected to lose 20 percent of employment, sparking much distress. Previous research shows that stress affects pregnancy and fetal development. I find that immediately following the announcement, the mean gestational age in the most affected areas dropped by 1.5 days for a period of 1-2 months. Births shifted from 39 to 37-38 weeks, a period linked to health risks. Similar changes appear in birth weight. Local changes in employment and mothers’ characteristics do not account for these effects.
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Fear Itself: The Effects of Distressing Economic News on Birth Outcomes
Kyle Carlson
Caltech Working Paper, March 2014
Abstract:
I use new administrative data on mass layoffs and plant closings to study the effects of distressing economic news. Exposure to stressful events during pregnancy can impair fetal development. I find that announcement of impending job losses leads to a transient decrease in the mean birth weight within the firm’s county 1–4 months before the job losses. A loss of 500 jobs corresponds roughly to a decrease of 15–20 grams and 16 percent greater risk of low birth weight. Further analyses show that the initial effect results from curtailment of gestation, while slower intrauterine growth plays a later role.
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The Effect of Prenatal Natural Disaster Exposure on School Outcomes
Sarah Fuller
Demography, August 2014, Pages 1501-1525
Abstract:
This study looks at the impact of exposure to natural disasters during pregnancy on the educational outcomes of North Carolina children at the third grade level. A broad literature relates negative birth outcomes to poor educational performance, and a number of recent studies have examined the effect of prenatal exposure to natural disasters on birth outcomes. This study takes the next step by considering how prenatal exposure affects later outcomes. Combining North Carolina administrative data on births and school performance with disaster declarations from the U.S. Federal Emergency Management Agency (FEMA) allows for the identification of children who were exposed to disasters during prenatal development. These children are compared with other children born in the same county who were not exposed to disasters while in utero. Regression results suggest that children exposed to hurricanes prenatally have lower scores on third grade standardized tests in math and reading. Those exposed to flooding or tornadoes also have somewhat lower math scores. Additionally, results suggest that these negative effects are more concentrated among children in disadvantaged subgroups, especially children born to black mothers. However, no evidence exists that these effects are mediated by common measures of birth outcomes, including birth weight and gestational age.
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Upper-body strength predicts hunting reputation and reproductive success in Hadza hunter-gatherers
Coren Lee Apicella
Evolution and Human Behavior, forthcoming
Abstract:
Hunting is a characteristic feature of early human subsistence and many theories of evolution have emphasized the role of hunting in hominization. Still today hunting ability continues to be selected for in extant foragers with better hunters experiencing greater reproductive success. Yet little is known about the traits that comprise a successful hunter, traits that are presupposed to also be under selection. Two complementary empirical analyses were conducted to examine this question using data collected from Hadza hunter-gatherers in Tanzania. First, data on upper-body strength, running speed, target precision and visual and auditory acuity were collected to examine the traits that predict hunting reputation in men. Second, interview data were also collected from Hadza informants about the traits they deem important for hunting. Results from the first study implicate upper-body strength as the strongest and most consistent predictor of men’s hunting reputation. Hadza conventional wisdom also accord with these findings. Although informants stressed the importance of non-physical traits, such as “intelligence” and “heart”, strong arms were cited as the most important physical trait for hunting. Finally, men with stronger upper-bodies experienced greater reproductive success, a result that is largely mediated by hunting reputation. These findings suggest that selection for hunting ability may have acted on men’s upper-bodies. Nevertheless, the importance of effort on strength and hunting success cannot be dismissed. This is also discussed.
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Emily Grundy & Øystein Kravdal
Journal of Epidemiology & Community Health, forthcoming
Background: Short and very long interbirth intervals are associated with worse perinatal, infant and immediate maternal outcomes. Accumulated physiological, mental, social and economic stresses arising from raising children close in age may also mean that interbirth intervals have longer term implications for the health of mothers and fathers, but few previous studies have investigated this.
Methods: Discrete-time hazards models were estimated to analyse associations between interbirth intervals and mortality risks for the period 1980–2008 in complete cohorts of Norwegian men and women born during 1935–1968 who had had two to four children. Associations between interbirth intervals and use of medication during 2004–2008 were also analysed using ordinary least-squares regression. Covariates included age, year, education, age at first birth, parity and change in coparent since the previous birth.
Results: Mothers and fathers of two to three children with intervals between singleton births of less than 18 months, and mothers of twins, had raised mortality risks in midlife and early old age relative to parents with interbirth intervals of 30–41 months. For parents with three or four children, longer average interbirth intervals were associated with lower mortality. Short intervals between first and second births were also positively associated with medication use. Very long intervals were not associated with raised mortality or medication use when change of coparent since the previous birth was controlled.
Conclusions: Closely spaced and multiple births may have adverse long-term implications for parental health. Delayed entry to parenthood and increased use of fertility treatments mean that both are increasing, making this a public health issue which needs further investigation.
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Associations of Adolescent Hopelessness and Self-Worth With Pregnancy Attempts and Pregnancy Desire
Anna Fedorowicz et al.
American Journal of Public Health, August 2014, Pages e133-e140
Objectives: We examined the associations of pregnancy desire (ambivalence or happiness about a pregnancy in the next year) and recent pregnancy attempts with hopelessness and self-worth among low-income adolescents.
Methods: To evaluate independent associations among the study variables, we conducted gender-stratified multivariable logistic regression analyses with data derived from 2285 sexually experienced 9- to 18-year-old participants in the Mobile Youth Survey between 2006 and 2009.
Results: Fifty-seven percent of youths reported a desire for pregnancy and 9% reported pregnancy attempts. In multivariable analyses, hopelessness was positively associated and self-worth was negatively associated with pregnancy attempts among both female and male youths. Hopelessness was weakly associated (P = .05) with pregnancy desire among female youths.
Conclusions: The negative association of self-worth and the positive association of hopelessness with pregnancy attempts among young men as well as young women and the association of hopelessness with pregnancy desire among young women raise questions about why pregnancy is apparently valued by youths who rate their social and cognitive competence as low and who live in an environment with few options for material success.
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Fertility Decline and Missing Women
Seema Jayachandran
NBER Working Paper, June 2014
Abstract:
India's male-biased sex ratio has worsened over the past several decades. In combination with the increased availability of prenatal sex-diagnostic technology, the declining fertility rate is a hypothesized factor. Suppose a couple strongly wants to have at least one son. At the natural sex ratio, they are less likely to have a son the fewer children they have, so a smaller desired family size will increase the likelihood they manipulate the sex composition of their children. This paper empirically measures the relationship between desired fertility and the sex ratio. Standard survey questions on fertility preferences ask the respondent her desired number of children of each sex, but people who want larger families have systematically stronger son preference, which generates bias. This paper instead elicits desired sex composition at specified, randomly determined, levels of total fertility. These data allow one to isolate the causal effect of family size on the desired sex ratio. I find that the desired sex ratio increases sharply as the fertility rate falls; fertility decline can explain roughly half of the increase in the sex ratio that has occurred in India over the past thirty years. In addition, factors such as female education that lead to more progressive attitudes could counterintuitively cause a more male-skewed sex ratio because while they reduce the desired sex ratio at any given family size, they also reduce desired family size.
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Yvette Lamb et al.
Cognition, September 2014, Pages 461–470
Abstract:
Maternal stress during pregnancy has been associated with a range of adverse outcomes in offspring and the catechol-O-methyltransferase (COMT) gene has been linked to differential susceptibility to the consequences of antenatal stress. This study examined two functional polymorphisms of the COMT gene (rs4680 and rs165599) in relation to maternal perceived stress and childhood cognitive performance. Data from the longitudinal Auckland Birthweight Collaborative (ABC) study was used. Maternal perceived stress over the prior month was measured at birth, 3.5 and 7 years. Full-Scale IQ (FSIQ) was measured at ages 7 and 11. At age 11, a total of 546 DNA samples were collected from the child participants. Data were subjected to a series of split-plot ANCOVAs with birthweight for gestational age and maternal school leaving age as covariates. There were direct effects of maternal stress during the last month of pregnancy on offspring FSIQ at ages 7 and 11 years. A significant interaction revealed that children exposed to high maternal antenatal stress had significantly lower FSIQ scores at both 7 and 11 years of age than those exposed to low stress, only when they were carriers of the rs165599 G allele. At each age, this difference was of approximately 5 IQ points. The G allele of the rs165599 polymorphism may confer genetic susceptibility to negative cognitive outcomes arising from exposure to antenatal stress. This finding highlights the need to consider gene-environment interactions when investigating the outcomes of antenatal stress exposure.
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Saving Babies: The Impact of Public Education Programs on Infant Mortality
Carolyn Moehling & Melissa Thomasson
Demography, April 2014, Pages 367-386
Abstract:
We take advantage of unique data on specific activities conducted under the Sheppard-Towner Act from 1924 through 1929 to focus on how public health interventions affected infant mortality. Interventions that provided one-on-one contact and opportunities for follow-up care, such as home visits by nurses and the establishment of health clinics, reduced infant deaths more than did classes and conferences. These interventions were particularly effective for nonwhites, a population with limited access to physicians and medical care. Although limited data on costs prevent us from making systematic cost-benefit calculations, we estimate that one infant death could be avoided for every $1,600 (about $20,400 in 2010 dollars) spent on home nurse visits.
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Trade and fertility in the developing world: The impact of trade and trade structure
Thomas Gries & Rainer Grundmann
Journal of Population Economics, October 2014, Pages 1165-1186
Abstract:
In the literature on trade and development, fertility and trade have been widely discussed as two separate economic forces. However, an important recent contribution connects these two and suggests that international trade between developed and developing countries has an asymmetric effect on the demand for human capital. The asymmetry leads to a decline in fertility rates in developed countries and an increase in these rates in developing countries. We provide additional comprehensive empirical evidence in support of this novel hypothesis. Our findings suggest that countries that export skill-intensive manufacturing goods experience a decline in fertility rates, whereas in countries that export primary, low-skill-intensive goods, fertility rates are affected positively. Further, our findings indicate that the negative influence of manufacturing exports on fertility holds primarily and most strongly for middle-income countries where structural modernization and a growing manufacturing-intensive export sector is observed.
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Sue Ricketts, Greta Klingler & Renee Schwalberg
Perspectives on Sexual and Reproductive Health, forthcoming
Context: Long-acting reversible contraceptive (LARC) methods are recommended for young women, but access is limited by cost and lack of knowledge among providers and consumers. The Colorado Family Planning Initiative (CFPI) sought to address these barriers by training providers, financing LARC method provision at Title X–funded clinics and increasing patient caseload.
Methods: Beginning in 2009, 28 Title X–funded agencies in Colorado received private funding to support CFPI. Caseloads and clients’ LARC use were assessed over the following two years. Fertility rates among low-income women aged 15–24 were compared with expected trends. Abortion rates and births among high-risk women were tracked, and the numbers of infants receiving services through the Special Supplemental Nutrition Program for Women, Infants and Children (WIC) were examined.
Results: By 2011, caseloads had increased by 23%, and LARC use among 15–24-year-olds had grown from 5% to 19%. Cumulatively, one in 15 young, low-income women had received a LARC method, up from one in 170 in 2008. Compared with expected fertility rates in 2011, observed rates were 29% lower among low-income 15–19-year-olds and 14% lower among similar 20–24-year-olds. In CFPI counties, the proportion of births that were high-risk declined by 24% between 2009 and 2011; abortion rates fell 34% and 18%, respectively, among women aged 15–19 and 20–24. Statewide, infant enrollment in WIC declined 23% between 2010 and 2013.
Conclusions: Programs that increase LARC use among young, low-income women may contribute to declines in fertility rates, abortion rates and births among high-risk women.
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Sexual activity, endogenous reproductive hormones and ovulation in premenopausal women
Ankita Prasad et al.
Hormones and Behavior, July 2014, Pages 330–338
Abstract:
We investigated whether sexual activity was associated with reproductive function in the BioCycle Study, a prospective cohort study that followed 259 regularly menstruating women aged 18 to 44 years for one (n = 9) or two (n = 250) menstrual cycles in 2005–2007. Women were not attempting pregnancy nor using hormonal contraceptives. History of ever having been sexually active was assessed at baseline and frequency of sexual activity, defined as vaginal-penile intercourse, was self-reported daily throughout the study. Serum concentrations of estradiol, luteinizing hormone (LH), follicle-stimulating hormone (FSH), progesterone, and testosterone were measured up to 8 times/cycle. Sporadic anovulation was identified using peak progesterone concentration. Linear mixed models were used to estimate associations between sexual activity and reproductive hormone concentrations and generalized linear models were used to estimate associations with sporadic anovulation. Models were adjusted for age, race, body mass index, perceived stress, and alcohol consumption and accounted for repeated measures within women. Elevated concentrations of estrogen (+ 14.6%, P < .01), luteal progesterone (+ 41.0%, P < .01) and mid-cycle LH (+ 23.4%, P < .01), but not FSH (P = .33) or testosterone (P = .37), were observed in sexually active women compared with sexually inactive women (no prior and no study-period sexual activity); sexually active women had lower odds of sporadic anovulation (adjusted odds ratio = 0.34, 95% confidence interval: 0.16-0.73). Among sexually active women, frequency of sexual activity was not associated with hormones or sporadic anovulation (all P > .23). Findings from our study suggest that ever having been sexually active is associated with improved reproductive function, even after controlling for factors such as age.
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Haidong Wang et al.
Lancet, forthcoming
Background: Remarkable financial and political efforts have been focused on the reduction of child mortality during the past few decades. Timely measurements of levels and trends in under-5 mortality are important to assess progress towards the Millennium Development Goal 4 (MDG 4) target of reduction of child mortality by two thirds from 1990 to 2015, and to identify models of success.
Methods: We generated updated estimates of child mortality in early neonatal (age 0—6 days), late neonatal (7—28 days), postneonatal (29—364 days), childhood (1—4 years), and under-5 (0—4 years) age groups for 188 countries from 1970 to 2013, with more than 29 000 survey, census, vital registration, and sample registration datapoints. We used Gaussian process regression with adjustments for bias and non-sampling error to synthesise the data for under-5 mortality for each country, and a separate model to estimate mortality for more detailed age groups. We used explanatory mixed effects regression models to assess the association between under-5 mortality and income per person, maternal education, HIV child death rates, secular shifts, and other factors. To quantify the contribution of these different factors and birth numbers to the change in numbers of deaths in under-5 age groups from 1990 to 2013, we used Shapley decomposition. We used estimated rates of change between 2000 and 2013 to construct under-5 mortality rate scenarios out to 2030.
Findings: We estimated that 6.3 million (95% UI 6.0—6.6) children under-5 died in 2013, a 64% reduction from 17.6 million (17.1—18.1) in 1970. In 2013, child mortality rates ranged from 152.5 per 1000 livebirths (130.6—177.4) in Guinea-Bissau to 2.3 (1.8—2.9) per 1000 in Singapore. The annualised rates of change from 1990 to 2013 ranged from −6.8% to 0.1%. 99 of 188 countries, including 43 of 48 countries in sub-Saharan Africa, had faster decreases in child mortality during 2000—13 than during 1990—2000. In 2013, neonatal deaths accounted for 41.6% of under-5 deaths compared with 37.4% in 1990. Compared with 1990, in 2013, rising numbers of births, especially in sub-Saharan Africa, led to 1.4 million more child deaths, and rising income per person and maternal education led to 0.9 million and 2.2 million fewer deaths, respectively. Changes in secular trends led to 4.2 million fewer deaths. Unexplained factors accounted for only −1% of the change in child deaths. In 30 developing countries, decreases since 2000 have been faster than predicted attributable to income, education, and secular shift alone.
Interpretation: Only 27 developing countries are expected to achieve MDG 4. Decreases since 2000 in under-5 mortality rates are accelerating in many developing countries, especially in sub-Saharan Africa. The Millennium Declaration and increased development assistance for health might have been a factor in faster decreases in some developing countries. Without further accelerated progress, many countries in west and central Africa will still have high levels of under-5 mortality in 2030.
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Do fertility transitions influence infant mortality declines? Evidence from early modern Germany
Alan Fernihough & Mark McGovern
Journal of Population Economics, October 2014, Pages 1145-1163
Abstract:
The timing and sequencing of fertility transitions and early-life mortality declines in historical Western societies indicate that reductions in sibship (number of siblings) may have contributed to improvements in infant health. Surprisingly, however, this demographic relationship has received little attention in empirical research. We outline the difficulties associated with establishing the effect of sibship on infant mortality and discuss the inherent bias associated with conventional empirical approaches. We offer a solution that permits an empirical test of this relationship while accounting for reverse causality and potential omitted variable bias. Our approach is illustrated by evaluating the causal impact of family size on infant mortality using genealogical data from 13 German parishes spanning the sixteenth, seventeenth, eighteenth, and nineteenth centuries. Overall, our findings do not support the hypothesis that declining fertility led to increased infant survival probabilities in historical populations.