Abstract: This handbook chapter studies the theoretical microfoundations of urban agglomeration economies. We distinguish three types of micro-foundations, based on sharing, matching, and learning mechanisms. For each of these three categories, we develop one or more core models in detail and discuss the literature in relation to those models. This allows us to give a precise characterisation of some of the main theoretical underpinnings of urban agglomeration economies, to discuss modelling issues that arise when working with these tools, and to compare different sources of agglomeration economies in terms of the aggregate urban outcomes they produce as well as in terms of their normative implications. Key words: cities, agglomeration, increasing returns, micro-foundations jel classification: r12, r13, r32 ∗ This is a working draft of a chapter written for eventual publication in the Handbook of Regional and Urban Economics, Volume 4, edited by J. Vernon Henderson and Jacques-François Thisse, to be published by North-Holland. We are grateful to the editors, Masa Fujita, Mike Peters, and the participants at the the 2002 narsa meetings for comments and suggestions.

Abstract. In this paper, I examine the spatial correlation between wages and consumer purchasing power across U.S. counties to see whether regional demand linkages contribute to spatial agglomeration. First, I estimate a simple market-potential function, in which wages are associated with proximity to consumer markets. Second, I estimate an augmented market-potential function derived from the Krugman model of economic geography, parameter estimates for which reflect the importance of scale economies and transport costs. The estimation results suggest that demand linkages between regions are strong and growing over time, but quite limited in geographic scope. JEL Classification: F12, R12.

The identification of aggregate human-capital externalities is still not fully understood. The existing (Mincerian) approach confounds positive externalities with wage changes due to a downward sloping demand curve for human capital. As a result, the Mincerian approach yields positive externalities even when wages equal marginal social products. We propose an approach that identifies human-capital externalities, whether or not aggregate demand for human capital slopes downward. Another advantage of our approach is that it does not require estimates of the individual return to human capital. Applications to U.S. cities and states between 1970 and 1990 yield no evidence of significant average-schooling externalities.

We quantify agglomeration spillovers by estimating the impact of the opening of a large new manufacturing plant on the total factor productivity (TFP) of incumbent plants in the same county. Articles in the corporate real estate journal Site Selection reveal the county where the “Million Dollar Plant ” ultimately chose to locate (the “winning county”), as well as the one or two runner-up counties (the “losing counties”). The incumbent plants in the losing counties are used as a counterfactual for the TFP of incumbent plants in winning counties in the absence of the plant opening. Incumbent plants in winning and losing counties have economically and statistically similar trends in TFP in the 7 years before the opening, which supports the validity of the identifying assumption. After the new plant opening, incumbent plants in winning counties experience a sharp relative increase in TFP. Five years after the opening, TFP of incumbent plants in winning counties is 12 % higher than TFP of incumbent plants in losing counties. Consistent with some theories of agglomeration, this effect is larger for incumbent plants that share similar labor and technology pools with the new plant. We also find evidence of a relative increase in skill-adjusted labor costs in winning counties, indicating that the

The distribution of talent, or human capital, is an important factor in economic geography. This article examines the economic geography of talent, exploring the factors that attract talent and its effects on high-technology industry and regional incomes. Talent is defined as individuals with high levels of human capital, measured as the percentage of the population with a bachelor's degree and above. This article advances the hypothesis that talent is attracted by diversity, or what are referred to as low barriers to entry for human capital . To get at this, it introduces a new measure of diversity, referred to as the diversity index, measured as the proportion of gay households in a region. It also introduces a new measure of cultural and nightlife amenities, the coolness index, as well as employing conventional measures of amenities, high-technology industry, and regional income. Statistical research supported by the findings of interviews and focus groups is used to probe these issues. The findings confirm the hypothesis and shed light on both the factors associated with the economic geography of talent and its effects on regional development. The economic geography of talent is highly concentrated. Talent is associated with the diversity index. Furthermore, the economic geography of talent is strongly associated with high-technology industry location. Talent and high-technology industry work independently and together to generate higher regional incomes. In short, talent is a key intermediate variable in attracting high-technology industries and generating higher regional incomes.

concentration of college-educated residents was associated with a 0.8% increase in subsequent employment growth. Instrumental variables esti-mates support a causal relationship between college graduates and em-ployment growth, but show no evidence of an effect of high school graduates. Using data on growth in wages, rents, and house values, I calibrate a neoclassical city growth model and find that roughly 60 % of the employment growth effect of college graduates is due to enhanced productivity growth, the rest being caused by growth in the quality of life. This finding contrasts with the common argument that human capital generates employment growth in urban areas solely through changes in productivity. I.

Economic development and underdevelopment is one aspect of the uneven spatial distribution of economic activity. This paper reviews existing literature on geography and development, and argues that rigorous theoretical and empirical analysis is needed to increase understanding of the role of geography in development and to better design development policy. The analytical issues are: why does economic activity cluster in centers of activity? How do new centers develop? And what are the consequences of remoteness from existing centers? Empirical evidence comes both from the international context and from studies of internal economic geography and urbanization.

This paper exploits the division of Germany after the Second World War and the re-unification of East and West Germany in 1990 as a natural experiment to provide evidence of the importance of market access for economic development. In line with a standard new economic geography model, we find that following division cities in West Germany that were close to the new border between East and West Germany experienced a substantial decline in population growth relative to other West German cities. We provide several pieces of evidence that the decline of the border cities can be entirely accounted for by their loss in market access and is neither driven by differences in industrial structure nor differences in the degree of war-related disruption. Finally, we also find some first evidence of a recovery of the border cities after the re-unification of East and West Germany.

GDP growth is often measured poorly for countries and rarely measured at all for cities. We propose a readily available proxy: satellite data on lights at night. Our statistical framework uses light growth to supplement existing income growth measures. The framework is applied to countries with the lowest quality income data, resulting in estimates of growth that differ substantially from established estimates. We then consider a longstanding debate: do increases in local agricultural productivity increase city incomes? For African cities, we find that exogenous agricultural productivity shocks (high rainfall years) have substantial effects on local urban economic activity.

We review the accumulated knowledge on city size distributions and determinants of urban growth. This topic is of interest because of a number of key stylized facts, including notably Zipf’s law for cities (which states that the number of cities of size greater than S is proportional to 1/S) and the importance of urban primacy. We first review the empirical evidence on the upper tail of city size distribution. We offer a novel discussion of the important econometric issues in the characterization of the distribution. We then discuss the theories that have been advanced to explain the approximate constancy of the distribution across very different economic and social systems, emphasizing both bare-bone statistical theories and more developed economic theories. We discuss the more recent work on the determinants of urban growth and, in particular, growth regressions, economic explanations of city size distributions other than Gibrat’s law, consequences of major