Knowledge that Transforms

For social scientists, developing an empirical connection between the physical appearance of a city and the behavior and health of its inhabitants has proved challenging due to a lack of data on urban appearance. Can we use computers to quantify urban appearance from street-level imagery? We describe Streetscore: a computer vision algorithm that measures the perceived safety of streetscapes. Using Streetscore to evaluate 19 American cities, we find that the average perceived safety has a strong positive correlation with population density and household income; and the variation in perceived safety has a strong positive correlation with income inequality.

We combine a theoretical discrete-choice model of vehicle purchases, an econometric analysis of electricity emissions, and the AP2 air pollution model to estimate the geographic variation in the environmental benefits from driving electric vehicles. The second-best electric vehicle purchase subsidy ranges from $2,785 in California to −$4,964 in North Dakota, with a mean of −$1,095. Ninety percent of local environmental externalities from driving electric vehicles in one state are exported to others, implying they may be subsidized locally, even when the environmental benefits are negative overall. Geographically differentiated subsidies can reduce deadweight loss, but only modestly.

I estimate the effects of removing low-income youth with disabilities from Supplemental Security Income (SSI) on their earnings and income in adulthood. Using a regression discontinuity design based on a 1996 policy change in age 18 medical reviews, I find that youth who are removed from SSI at age 18 recover one-third of the lost SSI cash income in earnings. SSI youth who are removed and stay off SSI earn on average $4,400 annually, and they lose $76,000 in present discounted observed income over the 16 years following removal relative to those who do not receive a review.

We study the effect of top tax rates on “superstar” inventors' international mobility since 1977, using panel data on inventors from the US and European Patent Offices. We exploit the differential impact of changes in top tax rates on inventors of different qualities. Superstar inventors' location choices are significantly affected by top tax rates. In our preferred specification, the elasticity to the net-of-tax rate of the number of domestic superstar inventors is around 0.03, while that of foreign superstar inventors is around 1. These elasticities are larger for inventors in multinational companies. An inventor is less sensitive to taxes in a country if his company performs a higher share of its research there.

We show how size-contingent laws can be used to identify the equilibrium and welfare effects of labor regulation. Our framework incorporates such regulations into the Lucas (1978) model and applies this to France where many labor laws start to bind on firms with exactly 50 or more employees. Using data on the population of firms between 2002 and 2007 period, we structurally estimate the key parameters of our model to construct counterfactual size, productivity and welfare distributions. With flexible wages, the deadweight loss of the regulation is below 1% of GDP, but when wages are downwardly rigid welfare losses exceed 5%. We also show, regardless of wage flexibility, that the main losers from the regulation are workers (and to a lesser extent large firms) and the main winners are small firms.

This paper exploits quasi-experimental variation in tariffs in southern Africa to estimate trade elasticities. Traded quantities respond only weakly to a 30 percent reduction in the average nominal tariff rate. Trade flow data combined with primary data on firm behavior and bribe payments suggest that corruption is a potential explanation for the observed low elasticities. In contexts of pervasive corruption, even small bribes can significantly reduce tariffs, making tariff liberalization schemes less likely to affect the extensive and the intensive margins of firms' import behavior. The tariff liberalization scheme is, however, still associated with improved incentives to accurately report quantities of imported goods, and with a significant reduction in bribe transfers from importers to public officials.

Analysis of the timing of launches of 642 new drugs in 76 countries during 1983–2002 shows that patent and price regulation regimes strongly affect how quickly new drugs become commercially available in different countries. Price regulation delays launch, while longer and more extensive patent rights accelerate it. Health policy institutions and economic and demographic factors that make markets more profitable also speed up diffusion. The estimated effects are generally robust to controlling for endogeneity of policy regimes with country fixed effects and instrumental variables. The results highlight the important role of policy choices in driving the diffusion of new innovations.

We show that after monetary policy announcements, the conditional volatility of stock market returns rises more for firms with stickier prices than for firms with more flexible prices. This differential reaction is economically large and strikingly robust to a broad array of checks. These results suggest that menu costs—broadly defined to include physical costs of price adjustment, informational frictions, etc.—are an important factor for nominal price rigidity at the micro level. We also show that our empirical results are qualitatively and, under plausible calibrations, quantitatively consistent with New Keynesian macroeconomic models in which firms have heterogeneous price stickiness.

We explore the in- and out- of sample robustness of tests for choice inconsistencies based on parameter restrictions in parametric models, focusing on tests proposed by Ketcham, Kuminoff and Powers (KKP). We argue that their non-parametric alternatives are inherently conservative with respect to detecting mistakes. We then show that our parametric model is robust to KKP's suggested specification checks, and that comprehensive goodness of fit measures perform better with our model than the expected utility model. Finally, we explore the robustness of our 2011 results to alternative normative assumptions highlighting the role of brand fixed effects and unobservable characteristics.

We examine the pricing of financial crash insurance during the 2007–2009 financial crisis in US option markets, and we show that a large amount of aggregate tail risk is missing from the cost of financial sector crash insurance during the crisis. The difference in costs between out-of-the-money put options for individual banks and puts on the financial sector index increases four-fold from its precrisis 2003–2007 level. We provide evidence that a collective government guarantee for the financial sector lowers index put prices far more than those of individual banks and explains the increase in the basket-index put spread.