Uncertainty, ‘irrational exuberance’ and the psychology of bubbles: an argument over the legitimacy of financial regulation for bounded rational agents

One of the explanations for the Great Crisis of 2007-2008 was that financial authorities should have issued stricter regulations to prevent the housing bubble. However, according to Alan Greenspan, President of the Federal Reserve System (FED) from 1987 to 2006, this is to judge with hindsight. No one can guess when a “bubble” begins, nor when it ends; they happen because of the “irrational exuberance” in investors’ behavior, which causes boom and bust cycles. Regulators are not in a better situation for assessing risks, though: since market participants supposedly know their own risks better than the regulator (a kind of informational asymmetry), an intervention (except to ensure law-enforcement) would imply unjustified paternalism. However, a regulator does not have to be conceived as a paternalistic authority. We sketch an objection to Greenspan's argument, arguing that crises don’t require a defective reasoning such as the “irrational exuberance” – our usual bounded rationality might be enough to provide the kind of “self-fulfilling prophecy” observed in the rise and fall of bubble assets value. Given the possibility of grave externalities, authorities are justified in adopting measures to ensure investors behave in a prudent way, even if they supposedly know better their own risks.