This paper provides a systematic analysis of identification in linear social interactions models. This is a theoretical and econometric exercise as the analysis is linked to a rigorously delineated model of interdependent decisions. We develop an incomplete information game for individual choice under social influences that nests standard models as special cases. We consider identification of both endogenous and con-

This paper provides a systematic analysis of identification in linear social interactions models. This is both a theoretical and an econometric exercise as the analysis is linked to a rigorously delineated model of interdependent decisions. We develop an incomplete information game that describes individual choices in the presence of social interactions. The equilibrium strategy profiles are linear. Standard models in the empirical social interactions literature are shown to be exact or approximate special cases of our general framework, which in turn provides a basis for understanding the microeconomic foundations of those models. We consider identification of both endogenous (peer) and contextual social effects under alternative assumptions on a priori information about network structure available to an analyst, and contrast the informational content of individual-level and aggregated data. Finally, we discuss potential ramifications for identification of endogenous group selection and differences between the information sets of analysts and agents.

We study the effect of the world's largest school feeding program on children's learning outcomes. Staggered implementation across different states of a 2001 Indian Supreme Court Directive mandating the introduction of free school lunches in public primary schools generates plausibly exogenous variation in program exposure across different birth cohorts. We exploit this to estimate the effect of program exposure on math and reading test scores of primary school-aged children. We find that midday meals have a dramatic positive effect on learning achievement: children with up to 5 years of primary school exposure improve their test scores by approximately 10-20%. We further investigate various channels that may account for this improvement including enrollment and nutrition-learning effects, heterogeneous responses by socio-economic status, complementary schooling inputs, and intra-household redistribution. JEL-Codes: I210, I250, O120. in Burkina Faso find positive effects of school feeding programs on school participation. 2 In a rare non-randomized evaluation of an extant national program, McEwan (2013) uses a regression discontinuity design to study the effect of Chile's long-established school feeding program on (among other things) fourth-grade test scores. The discontinuity comes from the fact that students received meals with different caloric content depending on a school-level "vulnerability" index cutoff. McEwan (2013) finds that there is no difference in test performance when the caloric content of meals is increased.

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We study the effects of defaults on charitable giving in a large-scale field experiment on an online fundraising platform. We exogenously vary default options along two choice dimensions: the charitable donation decision and the “co-donation” decision regarding how much to contribute to supporting the platform. We document a strong effect of defaults on individual behavior but nevertheless find that aggregate donation levels are unaffected by defaults. In contrast, co-donations increase in the default amount. We complement our experimental results with a structural model that investigates whether personalizing defaults based on individuals' donation histories can increase donation revenues.