Families, primarily female-headed minority households with children, living in highpoverty public housing projects in five U.S. cities were offered housing vouchers by lottery in the Moving to Opportunity program. Four to seven years after random assignment, families offered vouchers lived in safer neighborhoods that had lower poverty rates than those of the control group not offered vouchers. We find no significant overall effects of this intervention on adult economic self-sufficiency or physical health. Mental health benefits of the voucher offers for adults and for female youth were substantial. Beneficial effects for female youth on education, risky behavior, and physical health were offset by adverse effects for male youth. For outcomes that exhibit significant treatment effects, we find, using variation in treatment intensity across voucher types and cities, that the relationship between neighborhood poverty rate and outcomes is approximately linear.

support. The authors are grateful to Yvonne Gastelum for collaborating on qualitative interviews in Spanish, Ying Qian for conducting pilot survey interviews and for compiling family contact information, Adriana Mendez for translating the survey into Spanish, Humberto Reynosa for editing the Spanish translation, and to Patrick Wang, Beth Welty and Lorin Obler for excellent research assistance. We thank all of the members of the MTO teams at MBHP, BHA, Abt and Westat for making our research possible, and Carol Luttrell for facilitating our access to administrative data. We have benefitted from conversations with numerous colleagues. We are particularly indebted to

Many important activities, such as charitable giving, voting, and paying taxes, are difficult to explain by the narrow self-interest hypothesis. In a large number of laboratory experiments, the self-interest hypothesis was rejected with respect to contributions to public goods (e.g., John O. Ledyard, 1995). Recent theories on pro-social behavior focus on “conditional cooperation”: people are assumed to be more willing to contribute when others contribute. This behavior may be due to various motivational reasons, such as conformity, social norms, or reciprocity. According to the theory of conditional cooperation, higher contribution rates are observed when information is provided that many others contribute. This prediction is not trivial: if people behave according to pure altruism theories (e.g., Charles Clotfelter, 1997), they reduce their own contribution when informed that others are already contributing. Testing for social comparison in the field encounters many difficulties (e.g., Charles Manski, 2000). For example, a positive correlation between expectations about the mean behavior of the reference group and one’s own behavior is consistent with conditional cooperation, but not conclusive, as causality is not clear. Behavior may influence expectations, and not the other way round. Only a few laboratory experiments circumvent these problems and explicitly test conditional cooperation (e.g., Urs Fischbacher et al., 2001). These studies conclude that roughly 50 percent of people increase their contribution if others do so as well. To our knowledge, this paper is the first to go further and to test conditional cooperation in a field experiment. 1 Our field experiment about charitable giving supports the theory of conditional cooperation: contributions increase, on average, if people know that many others contribute. The effect varies, however, depending on past contribution behavior. Those who never contributed do not change their behavior, while people who are indifferent about contributions react most strongly to information about others ’ behavior. Section I presents the field experiment and the empirical strategy to test the hypotheses, Section II shows the results, and Section III offers concluding remarks.

This paper surveys research on social capital. We explore the concepts that motivate the social capital literature, efforts to formally model social capital using economic theory, the econometrics of social capital, and empirical studies of the role of social capital in various socioeconomic outcomes. While our focus is primarily on the place of social capital in economics, we do consider its broader social science context. We argue that while the social capital literature has produced many insights, a number of conceptual and statistical problems exist with the current use of social capital by social scientists. We propose some ways to strengthen the social capital literature.

SOCIAL CAPITAL describes circumstances in which individuals can use membership in groups and networks to secure benefits. This formulation follows

Abstract. We investigate how and why the productivity of a worker varies as a function of the productivity of her co-workers in a group production process. In theory, the introduction of a high productivity worker could lower the effort of incumbent workers because of free riding; or it could increase the effort of incumbent workers because of peer effects induced by social norms, social pressure, or learning. Using scanner level data, we measure high frequency, worker-level productivity of checkers for a large grocery chain. Because of the firm‘s scheduling policy, the timing of within-day changes in personnel is unsystematic, a feature for which we find consistent support in the data. We find strong evidence of positive productivity spillovers from the introduction of highly productive personnel into a shift. A 10 % increase in average co-worker permanent productivity is associated with 1.7 % increase in a worker’s effort. Most of this peer effect arises from low productivity workers benefiting from the presence of high productivity workers. Therefore, the optimal mix of workers in a given shift is the one that maximizes skill diversity. In order to explain the mechanism that generates the peer effect, we examine whether effort depends on workers ’ ability to monitor one another due to their spatial arrangement, and whether effort is affected by the time workers have previously spent working together. We find that a given worker’s effort is positively related to the presence and speed of workers who face him, but not the presence and speed of workers whom he faces (and do not face him). In addition, workers

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(3):577-98, 1993) developed a matching method to study the geography of knowledge spillovers using patent citations, and found that knowledge spillovers are strongly localized. Their method matches each citing patent to a non-citing patent intended to control for the pre-existing geographic concentration of production. We show how the method of selecting the control group may induce spurious evidence of localized spillovers. This paper reassesses their findings using control patents selected under different criteria. Doing so eliminates evidence of strong intranational localization effects at the state and metropolitan levels, but leaves largely unaffected evidence of international localization effects. (JEL O310, O340)

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This paper surveys the modern economics literature on the role of neighborhoods in influencing socioeconomic outcomes. Neighborhood effects have been analyzed in a range of theoretical and applied contexts and have proven to be of interest in understanding questions ranging from the asymptotic properties of various evolutionary games to explaining the persistence of poverty in inner cities. As such, the survey covers a range of theoretical, econometric and empirical topics. One conclusion from the survey is that there is a need to better integrate findings from theory and econometrics into empirical studies; until this is done, empirical studies of the nature and magnitude of neighborhood effects are unlikely to persuade those skeptical about their importance.