Credit booms are perceived to fuel resource misallocation and often end in crises that are followed by protracted periods of low growth. This column investigates the macroeconomic effects of credit booms using a new theory of information production. The theory predicts that when the economy enters a collateral boom, the price of collateral rises and lenders rely more on collateralisation and less on information-producing screening of entrepreneurs. Empirical evidence based on US data confirms the model’s predictions.