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.

Should optimal income taxation change when firms have market power? We analyze how the planner can optimally tax labor income of workers and profits of entrepreneurs. We derive optimal tax rates that depend on markups and identify four distinct components: the Mirrleesian incentive effect, the Pigouvian tax correction of the negative externality of market power, redistribution through altered factor prices, and reallocation of output toward the most productive firms. We quantify the optimal tax for the US economy and provide concrete proposals how to use income taxation to redistribute income while incentivizing production in the presence of market power.