The incremental innovations that underly much of modern economic growth typically involve changes to one or more components of a complex product. This creates a tension. On the one hand, a principal would like an agent to contribute innovative components. On the other hand, ironing out...

International trade can have profound effects on domestic institutions. We examine this proposition in the context of medieval Venice circa 800-1350. We show that (initially exogenous) increases in long-distance trade enriched a large group of merchants and these merchants used their new-found...

Increasingly, a small number of low-wage countries such as China and India are involved in innovation -- not `big ideas' innovation, but the constant incremental innovations needed to stay ahead in business. We provide some evidence of this new phenomenon and develop a model in which there is a...

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...

There is controversy about whether geography matters mainly because of its contemporaneous impact on economic outcomes or because of its interaction with historical events. Looking at terrain ruggedness, we are able to estimate the importance of these two channels. Because rugged terrain hinders...

We develop an urban growth model where human capital spillovers foster entrepreneurship and learning in heterogenous cities. Incumbent residents limit city expansion through planning regulations so that commuting and housing costs do not outweigh productivity gains. The model builds on strong...

Urban density boosts productivity and innovation, improves access to goods and services, reduces typical travel distances, encourages energy-efficient construction and transport, and facilitates sharing scarce amenities. However, density is also synonymous with crowding, makes living and moving...

Striking evidence is presented of a previously unremarked transformation of urban structure from mainly sectoral to mainly functional specialization. We offer an explanation showing that this transformation is inextricably interrelated with changes in firms' organization. A greater variety of...

The difficulty of incorporating general equilibrium price effects into econometric estimating equations has deterred most researchers from econometrically estimating the welfare gains from trade liberalization. Using a paired-down CES monopolistic competition example, we show that this...

The two models of international trade with developed factor markets -- Heckscher-Ohlin and Specific Factors -- both suffer significant defects. For example, their predictions about the patterns of domestic production and international trade are for the most part either indeterminate or uselessly...