Knowledge that Transforms

The industrial cities of the 19th century were incredibly unhealthy places to live. How much progress has been made in reducing these negative health effects over the past 150 years? To help answer this question, we compare mortality patterns in 19th century England to those in Chinese urban areas in 2000. We document that substantial improvements have been made in improving health in cities over this period. Unlike historical English cities, large cities in China have lower mortality than less populated areas. However, we also provide evidence that in China a substantial relationship between industrial pollution and mortality remains.

Default contribution rates for 401(k) pension plans powerfully influence choices. Potential causes include opt-out costs, procrastination, inattention, and psychological anchoring. Using realistically parameterized models, we show how the optimal default, the magnitude of the welfare effects, and the degree of normative ambiguity depend on the behavioral model, the scope of the choice domain deemed welfare-relevant, the use of penalties for passive choice, and other 401(k) plan features. While results are theory-specific, our analysis provides reasonably robust justifications for setting the default either at the highest contribution rate matched by the employer or—contrary to common wisdom—at zero. (JEL D14, D91, J26, J32)

We analyze the welfare consequences of a monopolist having additional information about consumers' tastes, beyond the prior distribution; the additional information can be used to charge different prices to different segments of the market, i.e., carry out “third degree price discrimination.” We show that the segmentation and pricing induced by the additional information can achieve every combination of consumer and producer surplus such that: (i) consumer sur plus is nonnegative, (ii) producer surplus is at least as high as profits under the uniform monopoly price, and (iii) total surplus does not exceed the surplus generated by efficient trade. (JEL D42, D83, L12)

We investigate the relationship between political networks, weak institutions, and election fraud during the 2010 parliamentary election in Afghanistan combining: (i) data on political connections between candidates and election officials; (ii) a nationwide controlled evaluation of a novel monitoring technology; and (iii) direct measurements of aggregation fraud. We find considerable evidence of aggregation fraud in favor of connected candidates and that the announcement of a new monitoring technology reduced theft of election materials by about 60 percent and vote counts for connected candidates by about 25 percent. The results have implications for electoral competition and are potentially actionable for policymakers. (JEL C93, D02, D72, K42, O17)

Notwithstanding great progress in scientific and economic understanding of climate change, it has proven difficult to forge international agreements because of free-riding, as seen in the defunct Kyoto Protocol. This study examines the club as a model for international climate policy. Based on economic theory and empirical modeling, it finds that without sanctions against non-participants there are no stable coalitions other than those with minimal abatement. By contrast, a regime with small trade penalties on non-participants, a Climate Club, can induce a large stable coalition with high levels of abatement. (JEL Q54, Q58, K32, K33)

This paper considers the normative implications of technical change for tax policy design. A task-to-talent assignment model of the labor market is embedded into an optimal tax problem. Technical change modifies equilibrium wage growth across talents and the substitutability of talents across tasks. The overall optimal policy response is to reduce marginal income taxes on low to middle incomes, while raising those on middle to high incomes. The reform favors those in the middle of the income distribution, reducing their average taxes while lowering transfers to those at the bottom. (JEL D31, H21, H23, H24, J31, O33)

While present bias is an old idea, it only took hold in economics following David Laibson's (1994) dissertation. Over the past 20 years, research has led to a much better theoretical understanding of present bias, when and how to apply it, and which ancillary assumptions are appropriate in different contexts. Empirical analyses have demonstrated how present bias can improve our understanding of behavior in various economic field contexts. Nonetheless, there is still much to learn. In this paper, we give our assessment of some lessons learned, and to be learned.

This paper develops a theory that explains why financial crises follow profitable lending booms. When agents exhibit the “availability heuristic” and there is a long period of banking profitability, all agents—banks, their investors, and regulators—end up in an “availability cascade,” overestimating bankers' risk-management skills and underestimating the probability that observed outcomes are due to good luck. Consequently, banks profitably invest in riskier assets. Subsequently, if a public signal reveals that outcomes are luck-driven, investors withdraw funds, liquidity evaporates, and a crisis ensues. A loan resale market improves liquidity but increases the probability of a crisis.

It is very important to know how much we can extrapolate from a study's results. This paper examines the issue using data from impact evaluations in development.

I test the effect of harsher punishments and sanctions on driving under the influence (DUI). In this setting, punishments are determined by strict rules on blood alcohol content (BAC) and previous offenses. Regression discontinuity derived estimates suggest that having a BAC above the DUI threshold reduces recidivism by up to 2 percentage points (17 percent). Likewise having a BAC over the aggravated DUI threshold reduces recidivism by an additional percentage point (9 percent). The results suggest that the additional sanctions experienced by drunk drivers at BAC thresholds are effective in reducing repeat drunk driving. (JEL I12, K42, R41)