Endogenous Social Connections in Legislatures

We present a model of the U.S. Congress in which social connections among Congress members are endogenous and matter for their legislative activity. We propose a novel equilibrium concept for the network formation game that allows for a sharp characterization of equilibrium behavior and that yields a unique prediction under testable conditions. While the equilibrium is characterized by a large number of nonlinear equations, we show that the model can be structurally estimated by an appropriately designed Approximate Bayesian Computation method. Estimating the model using data from the 109th to 113th U.S. Congresses, we show that social connections are important for legislators' productivities and we identify some of the key determinants of social centralities in Congress.