Abstract: We assemble a new global database on motor vehicle travel speed in over 1,200 large cities in 152 countries. We then estimate comparable city-level indices of travel speed and congestion. Most of the variation in urban travel speed is across countries, not within. National income per capita explains most of this cross-country variation in speed. In rich countries, urban travel is roughly 50% faster than in poor countries. To investigate the link between economic development and mobility, we develop an urban model with endogenous travel, road infrastructure, and land area. The model provides an exact decomposition of how city size, infrastructure, and topography contribute to explaining why urban travel is faster in richer countries. We find that richer countries are faster, mainly because their cities have more major roads and wider land areas. These effects operate by increasing uncongested speed, not by reducing congestion.

Abstract: Fast public transit networks are widely believed to (i) attract more riders and reduce negative externalities of driving, and (ii) reduce inequality by improving mobility for the urban poor. But are the transit improvements that are most effective at increasing transit ridership also more equitable? Combining survey data with web-scraped counterfactual travel times for millions of trips across 49 large US cities, I estimate a model of travel mode and residential location choice. I characterize the heterogeneity across income groups and cities in commuters' marginal willingness to pay for access to faster transit and to increase their transit ridership. I find that higher-income transit riders sort more aggressively into the fastest transit routes and are, on average, willing to pay more for faster commutes. Improvements in transit speed are most effective at generating transit ridership and welfare gains where transit is already fast (relative to driving), in cities with a greater share of rail-based transit and where the gains are larger for higher-income commuters. Transit improvements benefit lower-income commuters more where transit is relatively slow, in cities with more bus transit, and where the overall marginal gains are small.

Abstract: What are the implications of mass transit improvements for residential income segregation within cities? I observe large income differences in households' usage of and residential proximity to `fast' versus `slow' transit (e.g. subways versus buses on shared lanes). Consistent with these observations, I propose a theoretical framework to characterize the relationship between travel mode choices and income segregation within cities. I find that transit improvements that would maximize transit ridership tend to reduce income segregation when improving `slow’ transit but increase income segregation when improving `fast’ transit. These results are consistent with recent trends in transit ridership and neighborhood incomes in US cities.

Abstract: We provide a novel approach to estimate the deadweight loss of congestion. We implement it for road travel in the city of Bogotá using information from a travel survey and counterfactual travel data generated from Google Maps. For the supply of travel, we find that the elasticity of the time cost of travel per unit of distance with respect to the number of travellers is on average about 0.06. It is close to zero at low levels of traffic, then reaches a maximum magnitude of about 0.20 as traffic builds up and becomes small again at high levels of traffic. This finding is in sharp contrast with extant results for specific road segments. We explain it by the existence of local streets which remain relatively uncongested and put a floor on the time cost of travel. On the demand side, we estimate an elasticity of the number of travellers with respect to the time cost of travel of -0.40. Although road travel is costly in Bogotá, these findings imply a small daily deadweight loss from congestion, equal to less than 1% of a day’s wage.

Abstract: We develop a methodology to estimate robust city-level vehicular speed indices, exactly decomposable into uncongested speed and congestion. We apply it to 180 Indian cities using 57 million simulated trips measured by a web mapping service. We verify the reliability of our simulated trips using a number of alternative data sources, including data on actual trips. We find wide variation in speed across cities that is driven more by differences in uncongested speed than congestion. Denser and more populated cities are slower, only in part because of congestion. Urban economic development is correlated with faster speed despite worse congestion.

Abstract: This paper studies how the expansion of segregated neighborhoods eroded black wealth in prewar American cities. Using a novel sample of matched addresses, we find that over a single decade rental prices soared by roughly 50 percent on city blocks that transitioned from all white to majority black. Meanwhile, pioneering black families paid a 28 percent premium to buy a home on a majority white block, after which their homes lost 10 percent of their value. These findings strongly suggest that segregated housing markets cost black families much of the gains associated with moving north during the Great Migration. 

Abstract: Despite the “1/N problem” associated with profit sharing, the empirical literature finds that sharing profits with workers has a positive impact on work team and firm performance. We examine one possible resolution to this puzzle by observing that, although the incentive to work harder under profit sharing is weak, it might be sufficient to motivate workers to report each other for shirking, especially if the workers are reciprocally-minded. Our model provides the rationale for this conjecture and we discuss the results of an experiment that confirms that profit sharing is most effective when peer reporting is possible.