We propose a theory of reputation to explain how investors rationally respond to mutual fund star ratings. A fund's performance is determined by its information advantage, which can be acquired but decays stochastically. Investors form beliefs about whether the fund is informed based on its past performance. We refer to such beliefs as fund reputation, which determines fund flows. As performance changes continuously, equilibrium fund reputation may take discrete values only and thus can be labeled with stars. Star upgrades thus imply reputation jumps, leading to discrete increases in flows and expected performance, although stars do not provide new information.

We examine the network of trading relationships between insurers and dealers in the over‐the‐counter (OTC) corporate bond market. Regulatory data show that one‐third of insurers use a single dealer, whereas other insurers have large dealer networks. Execution prices are nonmonotone in network size, initially declining with more dealers but increasing once networks exceed 20 dealers. A model of decentralized trade in which insurers trade off the benefits of repeat business and faster execution quantitatively fits the distribution of insurers' network size and explains the price–network size relationship. Counterfactual analysis shows that regulations to unbundle trade and nontrade services can decrease welfare.