Diego Puga

Micro-Foundations of Urban Agglomeration Economies

This handbook chapter studies the theoretical micro-foundations 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.

The Rise and Fall of Regional Inequalities

This paper analyses how the degree of regional integration affects regional differences in production structures and income levels. With high transport costs, industry is spead across regions to meet final consumer demad. As transport costs fall, increasing returns interacting with labour mobility and/or inout-output linkages between firms create a tendency for the agglomeration of increasing returns activities. When workers migrate towards locations with more firms and higher real wages, this intensifies agglomeration. When instead workers do not move across regions, further reductions in transport costs make firms increasingly sensitive to wage differentials, leading industry to spread out again.

Agglomeration in the Global Economy: A Survey of the 'New Economic Geography'

This review of recent contributions reveals common conclusions about the effects of integration on location. For high trade costs the need to supply markets locally encourages firms to spread across different regions. Integration weakens the incentives for self-sufficiency and for intermediate values of trade costs pecuniary externalities induce firms and workers to cluster together, turning location into a self-reinforcing process. Agglomeration raises the price of immobile local factors and goods, however, so for low transport costs, firms may spread to regions where those prices are lower.

Diversity and Specialisation in Cities: Why, Where and When Does it Matter?

Why are some cities specialised and others diversified? What are the advantages and disadvantages of urban specialisation and diversity? To what extent does the structure of cities, and the activities of firms and people in them, change over time? How does the sectoral composition of cities influence their evolution? To answer these and related questions, we first distil some key stylised facts from the empirical literature on cities and the composition of their activities. We then turn to a review of different theories looking at such issues, and study the extent to which these theories contribute to the understanding of the empirical regularities.

The Magnitude and Causes of Agglomeration Economies

ABSTRACT Firms and workers are much more productive in large and dense urban environments. There is substantial evidence of such agglomeration economies based on three approaches. First, on a clustering of production beyond what can be explained by chance or comparative advantage. Second, on spatial patterns in wages and rents. Third, on systematic variations in productivity with the urban environment. However, more needs to be learned about the causes of agglomeration economies. We have good models of agglomeration through sharing and matching, but not a deep enough understanding of learning in cities. Despite recent progress, more work is needed to distinguish empirically between alternative causes.

Ruggedness: The Blessing of Bad Geography in Africa

We show that geography, through its impact on history, can have important effects on economic development today. The analysis focuses on the historic interaction between ruggedness and Africas slave trades. Although rugged terrain hinders trade and most productive activities, negatively affecting income globally, rugged terrain within Africa afforded protection to those being raided during the slave trades. Since the slave trades retarded subsequent economic development, ruggedness within Africa has also had a historic indirect positive effect on income. Studying all countries worldwide, we estimate the differential effect of ruggedness on income for Africa. We show that the differential effect of ruggedness is statistically significant and economically meaningful, it is found in Africa only, it cannot be explained by other factors like Africas unique geographic environment, and it is fully accounted for by the history of the slave trades.

The Productivity Advantages of Large Cities: Distinguishing Agglomeration from Firm Selection

Firms are more productive on average in larger cities. Two main explanations have been offered: firm selection (larger cities toughen competition, allowing only the most productive to survive) and agglomeration economies (larger cities promote interactions that increase productivity), possibly reinforced by localised natural advantage. To distinguish between them, we nest a generalised version of a tractable firm selection model and a standard model of agglomeration. Stronger selection in larger cities left-truncates the productivity distribution whereas stronger agglomeration right-shifts and dilates the distribution. Using this prediction, French establishment level data, and a new quantile approach, we show that firm selection cannot explain spatial productivity differences. This result holds across sectors, city size thresholds, establishment samples, and area definitions.

Agglomeration and Economic Development: Import Substitution vs. Trade Liberalisation

This paper analyses a model of economic development in which international inequalities in the location of industry and income are supported by the agglomeration of industry in a subset of countries. Economic development may not be a gradual process of convergence by all countries, but instead involves countries moving sequentially from the group of poor countries to the group of rich countries. The role of trade policy in promoting industrialization is studied. While both import substitution and unilateral trade liberalization may be ‘successful’ in attracting industry, they attract different sectors and welfare levels are higher under trade liberalization.

The Growth of Cities

Why do cities grow in population, surface area, and income per person? Which cities grow faster and why? To these questions, the urban growth literature has offered a variety of answers. Within an integrated framework, this chapter reviews key theories with implications for urban growth. It then relates these theories to empirical evidence on the main drivers of city growth, drawn primarily from the United States and other developed countries. Consistent with the monocentric city model, fewer roads and restrictions on housing supply hinder urban growth. The fact that housing is durable also has important effects on the evolution of cities. In recent decades, cities with better amenities have grown faster. Agglomeration economies and human capital are also important drivers of city growth. Although more human capital, smaller firms, and a greater diversity in production foster urban growth, the exact channels through which those effects percolate are not clearly identified. Finally, shocks also determine the fate of cities. Structural changes affecting the broader economy have left a big footprint on the urban landscape. Small city-specific shocks also appear to matter, consistent with the recent wave of random growth models.

Urbanization patterns: European versus less developed countries.

This paper develops a model in which the interaction between transport costs, increasing returns to scale, and labor migration across sectors and regions creates a tendency for urban agglomeration. Demand from rural areas favors urban dispersion. European urbanization took place mainly in the 19th century, with higher costs of spatial interaction, weaker economies of scale, and a less-elastic supply of labor to the urban sector than in less developed countries (LDCs) today. These factors could help explain why primate cities dominate in LDCs, whereas a comparatively small share of urban population lives in Europes largest cities.