Estimating the social return to transport infrastructure: A price-difference approach applied to a quasi-experiment

► An investment that doubled the capacity of a 1000-mile railroad in western China. ► The railroad was congested in only one direction before the capacity expansion. ► Using changes in price gaps between markets to infer the return to the investment. ► Price gaps decreased by 30% in the congestion direction, but not the other. ► An implied social return of 30% on average.