Market institutions, including institutions in the political marketplace, are created to facilitate the ability of individuals to exchange for their mutual benefit. This chapter begins with an analysis of markets for goods and services, with the idea that those same principles of market exchange carry over into political markets. A general equilibrium framework is used to depict the outcome of exchange under the assumption that there are no transaction costs to impede mutually advantageous exchanges. That model is institution-free, so the chapter continues to analyze what institutions would be necessary to produce that general equilibrium outcome in an environment in which there are transaction costs. The chapter notes that institutions have three economic functions: lowering transaction costs, enforcing rights and contracts, and redistribution. The chapter analyzes those first two functions, deferring a discussion of redistribution until Chapter 8.