Hoyt Bleakley

Language Skills and Earnings: Evidence from Childhood Immigrants.

Research on the effect of language skills on earnings is complicated by the endogeneity of language skills. This study exploits the phenomenon that younger children learn languages more easily than older children to construct an instrumental variable for language proficiency. We find a significant positive effect of English proficiency on wages among adults who immigrated to the United States as children. Much of this effect appears to be mediated through education. Differences between non-English-speaking origin countries and English-speaking ones that might make immigrants from the latter a poor control group for nonlanguage age-at-arrival effects do not appear to drive these findings.

Malaria Eradication in the Americas: A Retrospective Analysis of Childhood Exposure.

This study uses the malaria-eradication campaigns in the United States (circa 1920), and in Brazil, Colombia and Mexico (circa 1955) to measure how much childhood exposure to malaria depresses labor productivity. The campaigns began because of advances in health technology, which mitigates concerns about reverse causality. Malarious areas saw large drops in the disease thereafter. Relative to non-malarious areas, cohorts born after eradication had higher income as adults than the preceding generation. These cross-cohort changes coincided with childhood exposure to the campaigns rather than to pre-existing trends. Estimates suggest a substantial, though not predominant, role for malaria in explaining cross-region differences in income.

Chronic Disease Burden and the Interaction of Education, Fertility,and Growth

This study considers the eradication of hookworm disease from the American South (circa 1910) as a test of the quantity-quality (Q-Q) framework of fertility. Eradication was principally a shock to the price of quality because of three factors: hookworm (i) depresses the return to human capital investment, (ii) had a very low case-fatality rate, and (iii) had negligible prevalence among adults. Consistent with the Q-Q model, we find a significant decline in fertility associated with eradication.

Disease and Development: Evidence from the American South

Hookworm and malaria, parasites that remain a significant public health threat in the tropical belt today, were endemic in the American South as late as the first half of the twentieth century. I discuss how the successful eradication of malaria and hookworm in the American South affected human-capital accumulation. I find that areas that had higher levels of (malaria or hookworm) infection prior to eradication experienced greater increases in school attendance and literacy afterwards. Moreover, I find that adults earned substantially more if they were not exposed to these diseases as children. The estimates are large relative to the subsequent convergence between the North and South in the United States, but small compared to the cross-country distribution of income. Nevertheless, the results indicate potentially large benefits of public health interventions in developing countries. (JEL: I12, J24, O10, H43) Copyright (c) 2003 The European Economic Association.

The Effects of English Proficiency among Childhood Immigrants: Are Hispanics Different?

We test whether the effect of English proficiency differs between Hispanic and non-Hispanic immigrants. Using 2000 US Census microdata on immigrants who arrived before age 15, we relate labor market, education, marriage, fertility, and location of residence variables to their age at arrival in the US, and in particular whether that age fell within the “critical period” of language acquisition. We interpret the observed difference in outcomes between childhood immigrants who arrive during the critical period and those who arrive later (adjusted for non-language-related age-at-arrival effects using childhood immigrants from English-speaking countries) as an effect of English-language skills and construct an instrumental variable for English-language skills. We find that both Hispanics and non-Hispanics exhibit lower English proficiency if they arrive after the critical period, but this drop in English proficiency is larger for Hispanics. The effect of English proficiency on earnings and education is nevertheless quite similar across groups, while some differences are seen for marriage, fertility, and location of residence outcomes. In particular, although higher English proficiency reduces (for both groups) the number of children and the propensity to be married, marry someone with the same birthplace or origin, and live in an “ethnic enclave,” these effects are smaller for Hispanics.

Adapting to the Weather: Lessons from U.S. History

An important unknown in understanding the impact of climate change is the scope of adaptation, which requires observations on historical time scales. We consider how weather across U.S. history (1860-2000) has affected various measures of productivity. Using cross-sectional and panel methods, we document significant responses of agricultural and individual productivity to weather. We find strong effects of hotter and wetter weather early in U.S. history, but these effects have been attenuated in recent decades. The results suggest that estimates from a given period may be of limited use in forecasting the longer-term impacts of climate change.