This essay offers a mostly rational account for financial crises, centering on the 2008 crisis as an example. Market participants may overestimate the duration of high productivity growth due to new technologies and produce occasional—and likely unavoidable—bubbles. Considering potential changes in the regulation of financial markets, the conclusion is grim. Regulators have exhausted the effective legal levers against overestimations of continued high growth. The legislative responses to the last few crises were unproductive and pro-cyclical whereas public finance needs a counter-cyclical approach, souring euphorias and spurring out of slumps. A meaningful improvement would be the constitutional movement of financial legislative authority to a body with the independence to be counter-cyclical.