Knowledge that Transforms

When will solidarity, which emerges spontaneously from the fear of spillovers, be reinforced through contracting? The optimal pact between countries that differ substantially in their probability of distress is a simple debt contract with market financing, a borrowing cap, but no joint liability. While joint liability augments total surplus, the borrowing country cannot compensate the deep-pocket guarantor. By contrast, the optimal pact between two countries symmetrically exposed to shocks with an arbitrary correlation is a simple debt contract with joint liability, provided that shocks are sufficiently independent, spillovers sufficiently large, liquidity needs moderate, and available sanctions sufficiently tough. (JEL D86, F34, H63)

Suppose a policymaker is interested in the impact of an existing social program. Impact estimates using observational data suffer potential bias, while unbiased experimental estimates are often limited to other contexts. This creates a practical trade-off between internal and external validity for evidence-based policymaking. We explore this trade-off empirically for several common policies analyzed in development economics, including microcredit, migration, and education interventions. Based on mean-squared error, non-experimental evidence within context outperforms experimental evidence from another context. This advantage declines, but may not reverse, with experimental replication. We offer four reasons these findings are of general relevance to policy evaluation.

This paper examines the relationship between income, pollution, and mortality in China from 1991-2012. Using first-difference models, we document a robust positive association between city-level GDP and life expectancy. We also find a negative association between city-level particulate air pollution exposure and life expectancy that is driven by elevated cardiorespiratory mortality rates. The results suggest that while China's unprecedented economic growth over the last two decades is associated with health improvements, pollution has served as a countervailing force.

In the United States in the late 19th and early 20th century, large cities had extremely high death rates from infectious disease. Within major cities such as New York City and Philadelphia, there was significant variation at any point in time in the mortality rate across neighborhoods. Between 1900 and 1930 neighborhood mortality convergence took place in New York City and Philadelphia. We document these trends and discuss their consequences for neighborhood quality of life dynamics and the economic incidence of who gains from effective public health interventions.

We survey and apply several techniques from the statistical and computer science literature to the problem of demand estimation. To improve out-of-sample prediction accuracy, we propose a method of combining the underlying models via linear regression. Our method is robust to a large number of regressors; scales easily to very large data sets; combines model selection and estimation; and can flexibly approximate arbitrary non-linear functions. We illustrate our method using a standard scanner panel data set and find that our estimates are considerably more accurate in out-of-sample predictions of demand than some commonly used alternatives.

I study an economy where asymmetric information about the quality of capital endogenously determines liquidity. Liquid funds are key to relaxing financial constraints on investment and employment. These funds are obtained by selling capital or using it as collateral. Liquidity is determined by balancing the costs of obtaining liquidity under asymmetric information against the benefits of relaxing financial constraints. Aggregate fluctuations follow increases in the dispersion of capital quality, which raise the cost of obtaining liquidity. An estimated version of the model can generate patterns for quantities and credit conditions similar to the Great Recession. (JEL D82, E22, E24, E32, E44, G01)

In Capital in the Twenty-First Century, Thomas Piketty uses the market value of tradable assets to measure both productive capital and wealth. As a measure of wealth this is problematic because it ignores the value of human capital and transfer wealth, which have grown enormously over the last 300 years. Thus the constancy of the wealth/income ratio as portrayed in his data is an illusion. Further, the types of wealth that he does not measure are more equally distributed than tradable assets. The approach also incorrectly identifies capital gains due to reduced discount rates as increases in the capital stock.

The ability of web-based retailers to learn about and provide targeted consumer experiences is touted as an important distinction from traditional retailers. In principal, web-based insurance exchanges could benefit from these advantages. Using data from a large-scale experiment by a private sector health insurance exchange we estimate the returns to experimentation and targeted messaging. We find significant improvements in conversions in one treatment tested. Underlying the average impact were both intertemporal and demographic heterogeneity. We estimate that learning and targeted messaging could increase insurance applications by approximately 13 percent of the baseline conversion rate.

Gary Becker was one of the greatest thinkers of the 20th century. He advanced social science by introducing economic thinking into areas that were thought to be off limits. Because his theory was motivated by his desire to explain the world, his analyses were highly policy relevant. His work on discrimination, deterrence of crime, fertility, human capital, and the family all produced implications that were testable and verified by his and others' empirical research. Equally important, each research area provided policy guidance and many of his ideas have been implemented by government and non-government organizations.

Andreoni and Sprenger (2012a,b) observe that utility functions are distinct for risk and time preferences, and show that their findings are consistent with a preference for certainty. We revisit this question in an enriched experimental setting in which subjects make intertemporal decisions under different risk conditions. The observed choice behavior supports a separation between risk attitude and intertemporal substitution rather than a preference for certainty. We further show that several models, including Epstein and Zin (1989); Chew and Epstein (1990); and Halevy (2008) exhibit such a separation and can account for the overall experimental findings. (JEL C91, D81, D91)