Firms' location decisions often drive economic models of agglomeration, so distinguishing the causes of agglomeration requires understanding those decisions. Firms value proximity to (1) customers in market access models, (2) other firms as sources of positive externalities in production...

I show that equilibria exist in closed city-system models with production externalities if firms' production possibilities vary continuously with the source of the externality, are constant returns to scale in own inputs, include inaction, and satisfy free disposal; if firms have to employ their...

I demonstrate that in the monocentric city model, an allocation is in the core if and only if it is an equilibrium allocation, as long as households are endowed with strictly positive quantities of a composite consumption good, enjoy any net trade bundle at least as much as they enjoy one on the...