We develop a microstructure model of a market for a homogeneous good in which trade amongst heterogeneous consumers and producers is intermediated by middlemen and oligopolistic market makers (gatekeepers). Market makers post bid and ask prices which are freely observable. Middlemen stand ready...

This paper studies the endogenous structure of intermediation when heterogeneous intermediaries choose between becoming a middleman or a market maker, and the relation between the equilibrium market structure and price dispersion. We obtain three main results: First, middlemen and oligopolistic...