Prottoy Aman Akbar

Contact

4900 Wesley W. Posvar Hall
Pittsburgh, PA 15260

Job-market Paper

"Who Benefits from Faster Public Transit?"

Lower income commuters are more likely to ride and reside near public transit within cities, but do they also benefit more from faster transit travel? Combining survey data on travel behavior with web-scraped data on roads, establishments and counterfactual travel times for millions of trips across 49 US cities, I estimate a model of travel mode and residential location choices. I characterize the heterogeneity across income groups and cities in commuters' willingness to pay for access tofaster transit versus faster driving commutes. I find that richer commuters sort more aggressively into the fastest transit routes and are, on average, willing to pay more for faster travel. Improvements in transit speed are likely to attract and benefit high-income transit riders more where transit is fast (relative to driving) and in cities with a greater share of rail transit. Whereas they are likely to benefit low-income riders more where transit is relatively slow and in cities with more bus transit.

Other Works

Public Transit Access and Income Segregation 

Abstract: What are the implications of mass transit improvements for residential income segregation within cities? This paper models a stylized city where heterogeneous households choose where to live and how to travel given a spatial distribution of travel times and a competitive housing market. I characterize when and where marginal improvements in transit access reduce income segregation instead of exacerbating it. I show that a planner trying to maximize the city's transit ridership is incentivized to improve low-speed transit (e.g. buses on shared lanes) where it reduces income segregation but improve high-speed transit (e.g. subways) where it increases income segregation. These results are consistent with recent changes in transit ridership and neighborhood incomes in US cities. 

 

Mobility and Congestion in Urban India  

with Victor Couture (UC Berkeley), Gilles Duranton (UPenn) and Adam Storeygard (Tufts) 

(Revision requested at American Economic Review

Abstract: We develop a methodology to estimate robust city-level vehicular mobility indices, and apply it to 154 Indian cities using 22 million counterfactual trips measured by a web mapping service. There is wide variation in mobility across cities. An exact decomposition shows this variation is driven more by differences in uncongested mobility than congestion. Under plausible assumptions, a one-standard-deviation improvement in uncongested speed creates much more mobility than optimal congestion pricing. Denser and more populated cities are slower, only in part because of congestion. Urban economic development is correlated with better (uncongested and overall) mobility despite worse congestion. 

 

Racial Segregation in Housing Markets and the Erosion of Black Wealth 

with Sijie Li (Freddie Mac), Allison Shertzer (Pittsburgh) and Randall P. Walsh (Pittsburgh) 

Abstract: Housing is the most important asset for the vast majority of American households and a key driver of racial disparities in wealth. This paper studies how residential segregation by race eroded black wealth in prewar urban areas. Using a novel sample of matched addresses from prewar American cities, 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. These homes then lost 10 percent of their original value as the block became majority black. These findings strongly suggest that segregated housing markets cost black families much of the gains associated with migrating to the North. 

 

Measuring the Cost of Congestion in a Highly Congested City: Bogotá 

With Gilles Duranton (UPenn) 

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. 

 

Publication abstract and URL: 

Profit Sharing and Peer Reporting (2018), Management Science, 64(9), 4261-4276 

with Jeffrey Carpenter (Middlebury) and Andrea Robbett (Middlebury) 

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. 

 

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