This paper develops a theory that explains why financial crises follow profitable lending booms. When agents exhibit the “availability heuristic” and there is a long period of banking profitability, all agents—banks, their investors, and regulators—end up in an “availability cascade,” overestimating bankers' risk-management skills and underestimating the probability that observed outcomes are due to good luck. Consequently, banks profitably invest in riskier assets. Subsequently, if a public signal reveals that outcomes are luck-driven, investors withdraw funds, liquidity evaporates, and a crisis ensues. A loan resale market improves liquidity but increases the probability of a crisis.

We explain the use of legally unenforceable, discretionary financial contracts in circumstances where legally enforceable contracts are feasible. A discretionary contract allows a contracting party to choose whether or not to honor the contract. It is shown that such a contract liquefies reputational capital by permitting it to be depreciated in exchange for the preservation of financial capital and information reusability in financially impaired states. In addition, discretionary contracts foster the development of reputation. This explains discretion among highly confident letters, holding-company relationships, mutual-fund contracts, bank loan commitments, and other financial and nonfinancial contracts.