In a world of trade restrictions, large countries enjoy economic benefits, because political boundaries determine the size of the market. Under free trade and global markets even relatively small cultural, linguistic or ethnic groups can benefit from forming small, homogeneous political...

This paper studies the evolution of sectoral concentration in relation to the level of per capita income. We show that various measures of sectoral concentration follow a U-shaped pattern across a wide variety of data sources: countries first diversify, in the sense that economic activity is...

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...