This paper presents evidence from empirical studies that test hypotheses derived from models of household behavior pertaining to the interrelationships among population growth, human capital, and economic development. These studies have exploited quasi-natural experiments embodied in the cross-area variability in the wage rates of children in a number of low-income countries, the intercouple variation in the biological propensity to conceive, and the geographically selective introduction of new high-yielding seed varieties in India in the period 1961-71. The different varieties of evidence support the hypotheses that alterations in the returns to human capital associated with exogenous technical change lead simultaneously to increases in human capital investments and to reductions in fertility and that the costliness of fertility control is a significant but modest factor in inhibiting human capital investments.

This paper presents evidence from empirical studies that test hypotheses derived from models of household behavior pertaining to the interrelationships among population growth, human capital, and economic development. These studies have exploited quasi-natural experiments embodied in the cross-area variability in the wage rates of children in a number of low-income countries, the intercouple variation in the biological propensity to conceive, and the geographically selective introduction of new high-yielding seed varieties in India in the period 1961-71. The different varieties of evidence support the hypotheses that alterations in the returns to human capital associated with exogenous technical change lead simultaneously to increases in human capital investments and to reductions in fertility and that the costliness of fertility control is a significant but modest factor in inhibiting human capital investments.

A model is formulated incorporating linkages among nutrition, labor-market productivity, health heterogeneity, and the intrahousehold distribution of food and work activities in a subsistence economy. Empirical results, based on a sample of households from Bangladesh, indicate that, despite considerable intrahousehold disparities in calorie consumption, households are averse to inequality. Furthermore, consistent with the model, the results also indicate that both the higher level and greater variance in the calories consumed by men relative to women reflect in part the greater participation by men in activities in which productivity is sensitive to health status.

In a recent article in this Review (Borias, 1987), George Borjas uses a standard model of self-selection to demonstrate that immigrants in the United States may not necessarily be positively selected, as is commonly assumed. Borjas' empirical results, based on U.S. Census micro data merged with country-of-origin characteristics for 41 sending countries, however, do not provide clear or consistent results with respect to the immigration selection issue, although they do confirm earlier findings that the characteristics of the countries of origin of U.S. immigrants explain a substantial proportion of the differences in their economic status (Jasso and Rosenzweig, 1986b).' The purpose of this note is to show that Borjas' results are themselves subject to biases due to additional processes of self-selection. In particular, his inconclusive findings with respect to immigration selectivity arise from the use of a choice-based sample; enlargement of his highly selective sample of countries, based on the number of foreign-born in the United States, yields results that appear to conform much more closely and consistently to conventional wisdom, namely that the United States appears to attract those persons with above-average skills. We also provide evidence that changes in the earnings of aggregate immigrant entry cohorts, used by Borjas to measure the assimilation of immigrants, reflect another evidently important selection process, namely selective emigration. The effects of country characteristics on the wages of the foreign-born at entry (immigration selectivity) are thus not comparable to the effects of such variables on the changes in the characteristics of an immigrant cohort over time (emigration selectivity). The effects via immigration self-selection of country-of-origin characteristics on the Q of immigrants who migrate to a destination country is neatly summarized by Borjas in his equation (12). With unobservables determining earnings normally distributed, the expected quality of immigrants in the United States is given by