Relationship Trading in OTC Markets

We examine the network of trading relations between insurers and dealers in the over-the-counter corporate bond market. Comprehensive regulatory data shows that many insurers use only one dealer while the largest insurers have networks of up to forty dealers. Large insurers receive better prices than small insurers. However, execution costs are a non-monotone function of the network size, increasing once the network size exceeds 20 dealers. To understand these facts we build a model of decentralized trade in which insurers trade off the benefits of repeat business against dealer competition. The model can quantitatively fit the distribution of insurers' network sizes and how prices depend on insurers' size.