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.

On spatial dynamics.

It has long been recognized that the forces that lead to the agglomeration of economic activity and to aggregate growth are similar. Unfortunately, few formal frameworks have been advanced to explore this link. We critically discuss the literature and present a simple framework that can circumvent some of the main obstacles we identify.We discuss the main characteristics of an equilibrium allocation in this dynamic spatial framework, present a numerical example to illustrate the forces at work, and provide some supporting empirical evidence.

Organization and Inequality in a Knowledge Economy

We present a theory of the organization of work in an economy where knowledge is an essential input in production: a knowledge economy. In this economy a continuum of agents with heterogeneous skills must choose how much knowledge to acquire and may produce on their own or in organizations. Our theory generates an assignment of workers to positions, a wage structure, and a continuum of knowledge-based hierarchies. Organization allows low skill agents to ask others for directions. Thus, they acquire less knowledge than in isolation. In contrast, organization allows high skill agents to leverage their knowledge through large teams. Hence, they acquire more knowledge than on their own. As a result, organization decreases wage inequality within workers, but increases income inequality among the highest skill agents. We also show that equilibrium assignments and earnings can be interpreted as the outcome of alternative market institutions such as firms, or consulting and referral markets. We use our theory to study the impact of information and communication technology, and contrast its predictions with US evidence.

Spatial Growth and Industry Age

U.S. county data for the last 20 or 30 years show that manufacturing employment has been deconcentrating. In contrast, the service sector exhibits concentration in counties with intermediate levels of employment. This paper presents a theory where local sectoral growth is driven by technological diffusion across space. The age of an industry -- measured as the time elapsed since the last major general purpose technology innovation in the sector -- determines the pattern of scale dependence in growth rates. Young industries exhibit non-monotone relationships between employment levels and growth rates, while old industries experience negative scale dependence in growth rates. The model then predicts that the relationship between county employment growth rates and county employment levels in manufacturing at the turn of the 20th century should be similar to the same relationship in services in the last 20 years. We provide evidence consistent with this prediction.

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.

Spatial development

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 across locations. The result is a spatial 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 find that the model can generate the reduction in the employment share in manufacturing, the increase in service productivity starting in the second part of the 1990s, the increase in the value and dispersion of land rents in the same period, as well as several other spatial and temporal patterns.

On spatial dynamics.

It has long been recognized that the forces that lead to the agglomeration of economic activity and to aggregate growth are similar. Unfortunately, few formal frameworks have been advanced to explore this link. We critically discuss the literature and present a simple framework that can circumvent some of the main obstacles we identify. We discuss the main characteristics of an equilibrium allocation in this dynamic spatial framework, present a numerical example to illustrate the forces at work, and provide some supporting empirical evidence.Dynamic spatial models; Technology di usion; Spillovers; Trade; Factor Mobility; Growth;

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 diffuses 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 find 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.Dynamic Spatial Models, Growth, Innovation, Land Rent Evolution, Structural Transformation, Technology Diffusion, Trade