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.
Similarities between the Great Depression and the Great Recession are documented with respect to the behavior of financial markets. A Great Depression regime is identified by using a Markov-switching VAR. The probability of this regime has remained close to zero for many decades, but spiked for a short period during the most recent financial crisis, the Great Recession. The Great Depression regime implies a collapse of the stock market, with small-growth stocks outperforming small-value stocks. This helps to explain the cross section of asset returns when risk is priced according to a version of the "Bad Beta, Good Beta" Intertemporal CAPM that allows for regime changes.