In this paper, we demonstrate that, in a context where peer groups do not overlap fully, it is possible to identify all the relevant parameters of the standard linear-in-means model of social interactions. We apply this novel identification structure to study peer effects in the choice of college major. Results show that one is more likely to choose a major when many of her peers make the same choice. We also show that peers can divert students from majors in which they have a relative ability advantage, with adverse consequences on academic performance, entry wages, and job satisfaction. (JEL I23, J24, J31, Z13)

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The Policy Research Working Paper Series disseminates the findings of work in progress to encourage the exchange of ideas about development issues. An objective of the series is to get the findings out quickly, even if the presentations are less than fully polished. The papers carry the names of the authors and should be cited accordingly. The findings, interpretations, and conclusions expressed in this paper are entirely those of the authors. They do not necessarily represent the views of the International Bank for Reconstruction and Development/World Bank and its affiliated organizations, or those of the Executive Directors of the World Bank or the governments they represent.

We use an original data set covering 270 natural disasters to analyze the determinants of international emergency aid.Although humanitarian need appears to be a major determinant of emergency relief payments, our results suggest that political and strategic factors play a crucial role in emergency aid allocation as well. On average, donor governments favor smaller, geographically closer and oil exporting countries, and display significant biases in favor of politically less aligned countries as well as toward their former colonies. We also test and reject the independence of donors' aid decisions, finding strong evidence for bandwagon effects in humanitarian assistance.

In this paper we investigate whether peers' behavior influences the choice of college major, thus contributing to the mismatch of skills in the labor market. Using a newly constructed dataset, we are able to identify the endogenous effect of peers on such decisions through a novel identification strategy that solves the common econometric problems of studies of social interactions. Results show that, indeed, one is more likely to choose a major when many of her peers make the same choice. We also provide evidence on skills mismatch in terms of entry wages and occupation. We find that peers can divert students from majors in which they have a relative ability advantage, with adverse consequences on academic performance, entry wages and job satisfaction.