This is not a trivial issue. If using contacts seems to have little overall impact on labor market outcomes, then perhaps economic models of the labor market can safely ignore "embeddedness"-the connections and ties among individuals-without sacrificing explanatory power.

Key Words peer effects, social networks, social homophily, fixed effects models ■ Abstract Although there is a large literature on social capital, empirical estimates of the effect of social capital may be biased because of social homophily, the tendency of similar people to become friends with each other. Despite the methodological difficulties, a recent literature has emerged across several different disciplines that tries to estimate the causal effect of social capital. This paper reviews this recent empirical literature on social capital, paying close attention to the statistical and theoretical assumptions involved. Overall, there is evidence that genuine progress has been made in estimating the effect of social capital. The reviewed articles should provide useful examples for future research.

This paper uses social network and spatial data from the National Longitudinal Study of Adolescent Health (Add Health) to examine the effect of racial residential segregation on school friendship segregation in the U.S. The use of hierarchical models allows us to simultaneously estimate the effect of race, within-school spatial segregation, and school diversity on friendship choice using the Add Health data. We use these results to predict the decline in friendship segregation that would occur if across-and within-school residential segregation were eliminated in U.S. metropolitan areas. The results suggest that about a third of the level of racial friendship segregation in schools is attributable to residential segregation. Most of this effect is due to geographic segregation across schools rather than residential segregation within schools.

Occupations are central to the stratification systems of industrial countries, but they have played little role in empirical attempts to explain the well-documented increase in wage inequality that occurred in the United States in the 1980s and 1990s. We address this deficiency by assessing occupation-level effects on wage inequality using data from the Current Population Survey for 1983 through 2008. We model the mean and variance of wages for each occupation, controlling for education and demographic factors at the individual level to test three competing explanations for the increase in wage inequality: (1) the growth of between-occupation polarization, (2) changes in education and labor force composition, and (3) residual inequality unaccounted for by occupations and demographic characteristics. After correcting for a problem with imputed data that biased Kim and Sakamoto’s (2008) results, we find that between-occupation changes explain 66 percent of the increase in wage inequality from 1992 to 2008, although 23 percent of this is due to the switch to the 2000 occupation codes in 2003. Sensitivity analysis reveals that 18 percent of the increase in inequality from 1983 to 2002 is due to changes in just three occupations: managers “not elsewhere classified,” secretaries, and computer systems analysts.

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Recent observers have pointed to a growing polarization within the U.S. public over politicized moral issues-the so-called culture wars. DiMaggio, Evans, and Bryson studied trends over the past 25 years in American opinion on a number of critical social issues, finding little evidence of increased polarization; abortion is the primary exception. However, their conclusions are suspect because they treat ordinal or nominal scales as interval data. This article proposes new methods for studying polarization using ordinal data and uses these to model the National Election Study (NES) abortion item. Whereas the analysis of this item by DiMaggio et al. points to increasing polarization of abortion attitudes between 1972 and 1994, this article's analyses of these data offers little support for this conclusion and lends weight to their view that recent concerns over polarization are overstated.

Recent scholarship claims that bilingualism has a positive effect on the academic achievement of immigrant children. According to this perspective, growing up speaking two languages is beneficial because it stimulates cognitive development and allows immigrants a means of resisting unwanted assimilation. Immigrant children who are fluent bilinguals can use their native-language ability to maintain beneficial aspects of their ethnic culture while accommodating to the linguistic demands of an English-speaking society. Using data on first-and second-generation Asian American students from the 1988 National Educational Longitudinal Study, we test for these hypothesized effects of bilingualism. We find no evidence that bilingualism per se has a positive effect on achievement. Instead, speaking a native language with parents has a temporary positive effect if the parents are not proficient in English. These results indicate that the academic importance of bilingualism is transitional: The educational benefits of delaying linguistic assimilation exist only before immigrant parents achieve a moderate level of English-language proficiency. he relationship between bilingualism and academic achievement draws much attention from both social scientists and policymakers because of the large presence of bilingual students in the American school system. Although immigrant groups overwhelmingly tend to become native English speakers within several generations (Veltman 1983), the continued influx of immigrants has kept the number of children who speak non-English languages at high levels. In the * Direct all correspondence to Ted Mouw

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