Firms are more productive on average in larger cities. Two explanations have been offered: agglomeration economies (larger cities promote interactions that increase productivity) and firm selection (larger cities toughen competition allowing only the most productive to survive). To distinguish...

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...

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...

Despite large regional policy expenditures, regional inequalities in Europe have not narrowed substantially over the last two decades, and by some measures have even widened. Income differences across States have fallen, but inequalities between regions within each State have risen. European...

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...

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...

Increasingly, a small number of low-wage countries such as China and India are involved in incremental innovation. That is, they are responsible for resolving production-line bugs and suggesting product improvements. We provide evidence of this new phenomenon and develop a model in which there...

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...

We study the relationship between urban sprawl and obesity. Using data that tracks individuals over time, we find no evidence that urban sprawl causes obesity. We show that previous findings of a positive relationship most likely reflect a failure to properly control for the fact the individuals...