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...

We develop a dynamic model of transitions in and out of employment. A worker finds a job at an optimal stopping time, when a Brownian motion with drift hits a barrier. This implies that the duration of each worker's jobless spells has an inverse Gaussian distribution. We allow for arbitrary...