A growing literature suggests that high-income countries export high-quality goods. Two hypotheses may explain such specialization, with different implications for welfare, inequality, and trade policy. Fajgelbaum et al. formalize the Linder hypothesis that home demand determines the pattern of specialization and, therefore, predict that high-income locations export high-quality products. The factor-proportions model also predicts that skill-abundant, high-income locations export skill-intensive, high-quality products. Prior empirical evidence does not separate these explanations. I develop a model that nests both hypotheses and employ microdata on U.S. manufacturing plants’ shipments and factor inputs to quantify the two mechanisms’ roles in quality specialization across U.S. cities. Home-market demand explains as much of the relationship between income and quality as differences in factor usage.

Global phenomena, such as climate change, often have local impacts that are spatially correlated. We show that greater spatial correlation of productivities can increase international inequality by increasing the correlation between a country's productivity and its gains from trade. We confirm this prediction using a half-century of exogenous variation in the spatial correlation of agricultural productivities induced by a global climatic phenomenon. We introduce this general-equilibrium effect into projections of climate-change impacts that typically omit spatial linkages and therefore do not account for the global scope of climate change. We project greater international inequality, with higher welfare losses across Africa.

Leading empiricists and theorists of cities have recently argued that the generation and exchange of ideas must play a more central role in the analysis of cities. This paper develops the first system of cities model with costly idea exchange as the agglomeration force. The model replicates a broad set of established facts about the cross section of cities. It provides the first spatial equilibrium theory of why skill premia are higher in larger cities and how variation in these premia emerges from symmetric fundamentals.

We provide measures of ethnic and racial segregation in urban consumption. Using Yelp reviews, we estimate how spatial and social frictions influence restaurant visits within New York City. Transit time plays a first-order role in consumption choices, so consumption segregation partly reflects residential segregation. Social frictions also affect restaurant choices: individuals are less likely to visit venues in neighborhoods demographically different from their own. While spatial and social frictions jointly produce significant levels of consumption segregation, we find that restaurant consumption is only about half as segregated as residences. Consumption segregation owes more to social than spatial frictions.