Health and the Megacity: Urban Congestion, Air Pollution, and Birth Outcomes in Brazil.

We studied the health effects of economic development in heavily urbanized areas, where congestion poses a challenge to environmental conditions. We employed detailed data from air pollution and birth records around the metropolitan area of São Paulo, Brazil, between 2002 and 2009. During this period, the megacity experienced sustained growth marked by the increases in employment rates and ownership of durable goods, including automobiles. While better economic conditions are expected to improve infant health, air pollution that accompanies it is expected to do the opposite. To untangle these two effects, we focused on episodes of thermal inversion-meteorological phenomena that exogenously lock pollutants closer to the ground-to estimate the causal effects of in utero exposure to air pollution. Auxiliary results confirmed a positive relationship between thermal inversions and several air pollutants, and we ultimately found that exposure to inversion episodes during the last three months of pregnancy led to sizable reductions in birth weight and increases in the incidence of preterm births. Increased pollution exposure induced by inversions also has a significant impact over fetal survival as measured by the size of live-birth cohorts.

Heightened immigration enforcement impacts US citizens' birth outcomes: Evidence from early ICE interventions in North Carolina.

We examine how increased Immigration and Customs Enforcement (ICE) activities impacted newborn health and prenatal care utilization in North Carolina around the time Section 287(g) of the Immigration and Nationality Act was first being implemented within the state. Focusing on administrative data between 2004 and 2006, we conduct difference-in-differences and triple-difference case-control regression analysis. Pregnancies were classified by levels of potential exposure to immigration enforcement depending on parental nativity and educational attainment. Contrast groups were foreign-born parents residing in nonadopting counties and all US-born non-Hispanic parents. The introduction of the program was estimated to decrease birth weight by 58.54 grams (95% confidence interval [CI], -83.52 to -33.54) with effects likely following from reduced intrauterine growth. These results are shown to coexist with a worsening in the timing of initiation and frequency of prenatal care received. Since birth outcomes influence health, education, and earnings trajectories, our findings suggest that the uptick in ICE activities can have large socioeconomic costs over US-born citizens.

Means-Tested Safety Net Programs and Hispanic Families: Evidence from Medicaid, SNAP, and WIC.

Hispanic families have historically used means-tested assistance less than high-poverty peers, and one explanation for this may be that anti-immigrant politics and policies are a barrier to program participation. We document the participation of Hispanic children in three antipoverty programs by age and parental citizenship and the correlation of participation with state immigrant-based restrictions. Hispanic citizen children with citizen parents participate in Supplemental Nutrition Assistance Program (SNAP) and Medicaid more than Hispanic citizen children with noncitizen parents. Foreign-born Hispanic mothers use Medicaid less than their socioeconomic status would suggest. However, little evidence exists that child participation in Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) varies by mother's nativity: foreign-born mothers of Hispanic infants participate in WIC at higher rates than U.S.-born Hispanic mothers. State policies that restrict immigrant program use correlate to lower SNAP and Medicaid uptake among citizen children of foreign-born Hispanic mothers. WIC participation may be greater because it is delivered through nonprofit clinics, and WIC eligibility for immigrants is largely unrestricted.

Brazil's Missing Infants: Zika Risk Changes Reproductive Behavior.

Zika virus epidemics have potential large-scale population effects. Controlled studies of mice and nonhuman primates indicate that Zika affects fecundity, raising concerns about miscarriage in human populations. In regions of Brazil, Zika risk peaked months before residents learned about the epidemic and its relation to congenital anomalies. This spatiotemporal variation supports analysis of both biological effects of Zika infection on fertility and the effects of learning about Zika risk on reproductive behavior. Causal inference techniques used with vital statistics indicate that the epidemic caused reductions in birth cohort size of approximately one-quarter 18 months after Zika infection risk peaked but 10 months after public health messages advocated childbearing delay. The evidence is consistent with small but not statistically detectable biological reductions in fecundity, as well as large strategic changes in reproductive behavior to temporally align childbearing with reduced risk to infant health. The behavioral effects are larger for more-educated and older women, which may reflect facilitated access to information and to family planning services within high-risk, mosquito-infested urban locations as well as perceptions about the opportunity costs of risks to pregnancy and infant survival.

Early patterns of skill acquisition and immigrants' specialization in STEM careers.

We provide empirical evidence of immigrants' specialization in skill acquisition well before entering the US labor market. Nationally representative datasets enable studying the academic trajectories of immigrant children, with a focus on high-school course-taking patterns and college major choice. Immigrant children accumulate skills in ways that reinforce comparative advantages in nonlanguage intensive skills such as mathematics and science, and this contributes to their growing numbers in science, technology, engineering, and math (STEM) careers. These results are compatible with well-established models of skill formation that emphasize dynamic complementarities of investments in learning.

Economic Assimilation and Skill Acquisition: Evidence From the Occupational Sorting of Childhood Immigrants.

We study the economic assimilation of childhood immigrants to the United States. The linguistic distance between English and the predominant language in one's country of birth interacted with age at arrival is shown to be closely connected to occupational sorting in adulthood. By applying big-data techniques to occupations' detailed skill requirements, we provide evidence that childhood immigrants from English-distant countries who arrived after the primary school years reveal comparative advantages in tasks distinct from those for which (close to) Anglophone immigrants are better suited. Meanwhile, those who arrive at younger ages specialize in a bundle of skills very similar to that supplied by observationally equivalent workers. These patterns emerge even after we net out the effects of formal education. Such findings are compatible with the existence of different degrees of complementarity between relative English-learning potential at arrival and the acquisition of multiple capabilities demanded in the U.S. labor market (math/logic, socioemotional, physical, and communication skills). Consistent with the investment-complementarity argument, we show that linguistic distance and age at arrival also play a significant role on the choice of college major within this population.