When firms and people are located near each other in cities and in industrial clusters, they benefit in various ways, including by reducing the costs of exchanging goods and ideas. One might assume that these benefits would become less important as transportation and communication costs fall....

In this paper, the evolution of product differentiation in industries is modeled as the result of a cumulative cost-reduction process subject to spillovers in a differentiated oligopoly. Our results suggest that the long-run outcome is dependent on the intensity of spillovers and the shape of...

Support for massive investments in transportation infrastructure, possibly with a change in the share of spending on transit, seems widespread. Such proposals are often motivated by the belief that our infrastructure is crumbling, that infrastructure causes economic growth, that current funding...