Stress Tests and Bank Portfolio Choice∗

How informative should bank stress tests be? I use Bayesian persuasion to formalize stress tests and show that regulators can reduce the likelihood of a bank run by performing tests which are only partially informative. Optimal stress tests give just enough failing grades to keep passing grades credible enough to avoid runs. The worse the state of the banking system, the more stringent stress tests must be to prevent runs. I find that optimal stress tests, by reducing the probability of runs, reduce the optimal level of banks’ liquidity cushions. I also examine the impact of anticipated stress tests on banks’ ex ante incentive to invest in risky versus safe assets.