We use a simple theory of a system of cities to decompose the determinants of the city size distribution into three main components: efficiency, amenities, and frictions. Higher efficiency and better amenities lead to larger cities but also to greater frictions through congestion and other...

This paper shows how competition for land may lead firms to optimally innovate in spite of the market being perfectly competitive. When bidding for a location, firms can enhance their bid by investing in innovations that make the land more valuable. Firms are willing to innovate because the...

We present a theory of spatial development. Manufacturing and services firms located in a continuous geographic area choose each period how much to innovate. Firms trade subject to transport costs and technology diffuses spatially. We apply the model to study the evolution of the US economy in...

We propose a theory of the global production process that focuses on tradeable tasks, and use it to study how falling costs of offshoring affect factor prices in the source country. We identify a productivity effect of task trade that benefits the factor whose tasks are more easily moved...

This paper presents a theory of establishment size dynamics based on the accumulation of industry-specific human capital that simultaneously rationalizes the economy- wide facts on establishment growth rates, exit rates, and size distributions. The theory predicts that establishment growth and...

The equilibrium relationship between trade and the spatial distribution of economic activity is fundamental to the analysis of national and regional trade patterns, as well as to the effect of trade frictions. We study this relationship using a trade model with a continuum of regions, transport...