Many markets involve two groups of agents who interact via “platforms,” where one group’s benefit from joining a platform depends on the size of the other group that joins the platform. I present three models of such markets: a monopoly platform; a model of competing platforms where agents join a single platform; and a model of “competitive bottlenecks” where one group joins all platforms. The ...

SECTION 1 A 37-year-old man presented with a 7-month history of vertigo, nausea, dysphagia, right-sided tinnitus, and hearing loss. He denied headache, paresthesias, change in vision, or problems with cognition. He endorsed a history of progressive fatigue, generalized weakness, and poor libido. His symptoms left him functionally impaired and bedridden. His medical history was remarkable for dy...

This paper develops a multi-country model of international trade that provides a simple micro-foundation for buyer-seller relationships in trade. We explore a rich dataset that identifies buyers and sellers in trade and establish a set of basic facts that guide the development of the theoretical model. We use predictions of the model to examine the role of buyer heterogeneity in a market for fi...