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Cross-Border Spillover: U.S. Gun Laws and Violence in Mexico

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To what extent, and under what conditions, does access to arms fuel violent crime? To answer this question, we exploit a unique natural experiment: the 2004 expiration of the U.S. Federal Assault Weapons Ban exerted a spillover on gun supply in Mexican municipios near Texas, Arizona, and New Mexico, but not near California, which retained a pre-existing state-level ban. We find first that Mexican municipios located closer to the non-California border states experienced differential increases in homicides, gun-related homicides, and crime gun seizures after 2004 . . . 
Oeindrila Dube
 

Substitution Bias and External Validity: Why an innovative anti-poverty program showed no net impact

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The net impact of development interventions can depend on the availability of close substitutes to the intervention. We analyze a randomized trial of an innovative anti-poverty program in South India which provides “ultra-poor” households with inputs to create a new, sustainable livelihood. We find no statistically significant evidence of lasting net impact on consumption, income or asset accumulation. Instead, income from the new livelihood substituted for earnings from wage labor. A very similar intervention made a large difference elsewhere in South Asia, however, where wage labor alternatives were less compelling. The analysis highlights the roles of substitution bias and dropout bias in shaping evaluation results and delimiting external validity.
Jonathan Morduch, Shamika Ravi, and Jonathan Bauchet

Cultural Change as Learning: The Evolution of Female Labor Force Participation Over a Century.

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his paper investigates the role of changes in culture in generating the dramatic increase in married women’s labor force participation over the last century. It develops a dynamic model of culture in which individuals hold heterogeneous beliefs regarding the relative long-run payoffs for women who work in the market versus the home. These beliefs evolve endogenously via an intergenerational learning process. Women are assumed to learn about the long-term payoffs of working by observing (noisy) private and public signals. This process generically generates the S-shaped figure for female labor force participation found in the data . . . 
Raquel Fernandez

The Impact of Microcredit on the Poor in Bangladesh: Revisiting the Evidence

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We replicate and re-analyze the most influential study of microcredit impacts (Pitt and Khandker, 1998). That study was celebrated for showing that microcredit reduces poverty, a much hoped-for possibility (though one not confirmed by recent randomized controlled trials). We show that the original results on poverty reduction disappear after dropping outliers, or when using a robust linear estimator. Using a new program for estimation of mixed process maximum likelihood models, we show how assumptions critical for the original analysis, such as error normality, are contradicted by the data. We conclude that questions about impact cannot be answered in these data.
David Roodman and Jonathan Morduch

Poverty and Self-Control

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The absence of self-control is often viewed as an important correlate of persistent poverty. Using a standard intertemporal allocation problem with credit constraints faced by an individual with quasi-hyperbolic preferences, we argue that poverty damages the ability to exercise self-control. Our theory invokes George Ainslie’s notion of “personal rules,” interpreted as subgame-perfect equilibria of an intrapersonal game played by a time-inconsistent decision maker. Our main result pertains to situations in which the individual is neither so patient that accumulation is possible from every asset level, nor so impatient that decumulation is unavoidable from every asset level. Such cases always possess a threshold level of assets above which personal rules support unbounded accumulation, and a second threshold below which there is a “poverty trap” . . . 
B. Douglas Bernheim, Debraj Ray, and Sevin Yeltekin

Banks and Microbanks

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We combine two datasets to examine whether the scale of an economy’s banking system affects the profitability and outreach of microfinance institutions. We find evidence that competition matters. Greater bank penetration in the overall economy is associated with microbanks pushing toward poorer markets, as reflected in smaller average loans sizes and greater outreach to women. The evidence is particularly strong for microbanks that rely on commercial-funding, use traditional bilateral lending contracts (rather than group lending methods favored by microfinance NGOs), and take deposits. We consider plausible alternative explanations for the correlations, including relationships that run through the nature of the regulatory environment and the structure of the banking environment, but we fail to find strong support for these alternative hypotheses.
Robert Cull, Asli Demirgüç-Kunt and Jonathan Morduch