Spatial Development

We present a theory of spatial development. A continuum of locations in a geographic area choose each period how much to innovate (if at all) in manufacturing and services. Locations can trade subject to transport costs and technology di¤uses spatially across locations. The result is an endogenous growth theory that can shed light on the link between the evolution of economic activity over time and space. We apply the model to study the evolution of the U.S. economy in the last few decades and that the model can generate the reduction in the employment share in manufacturing, the increase in service productivity in the second part of the 1990s, the increase in land rents in the same period, as well as several other spatial and temporal patterns

Urban Growth

Urban growth refers to the process of growth and decline of economic agglomerations. The pattern of concentration of economic activity, and its evolution, has been found to be an important determinant, and in some cases the result, of urbanization, the structure of cities, the organization of economic activity, and national economic growth. The size distribution of cities is the result of the patterns of urbanization, which result in city growth and city creation. The evolution of the size distribution of cities is in turn closely linked to national economic growth.

Spin-offs and the Market for Ideas

We propose a theory of firm dynamics in which workers have ideas for new projects that can be sold in a market to existing firms or implemented in new firms: spin-offs. Workers have private information about the quality of their ideas. Because of an adverse selection problem, workers can sell their ideas to existing firms only at a price that is not contingent on their information. We show that the option to spin off in the future is valuable so only workers with very good ideas decide to spin off and set up a new firm. Since entrepreneurs of existing firms pay a price for the ideas sold in the market that implies zero expected profits for them, firms' project selection is independent of their size, which, under some assumptions, leads to scale-independent growth. The entry and growth process of firms in this economy leads to an invariant distribution that resembles the one in the US economy.

Spinoffs and the market for ideas

We present a theory of spinoffs in which the key ingredient is the originator’s private information concerning the quality of his new idea. Because quality is privately observed, by the standard adverse-selection logic, the market can at best offer a price that reflects the average quality of ideas sold. This gives the holders of above-average-quality ideas the incentive to spin off. We show that only workers with very good ideas decide to spin off, while workers with mediocre ideas sell them. Entrepreneurs of existing firms pay a price for the ideas sold in the market that implies zero expected profits for them. Hence, firms’ project selection is independent of firm size, which, under some additional assumptions, leads to scale-independent growth. The entry and growth process of firms leads to invariant firm-size distributions that resemble the ones for the U.S. economy and most of its individual industries.