Document Type


Publication Date

Spring 2011


Financial bubbles, Financial markets, Credit, Borrowing


Banking and Finance Law | Law and Economics


I argue that financial asset price bubbles and busts, such as those we have recently experienced in the mortgage and securities markets, are compatible with market efficiency, individual rationality, and even ethically unobjectionable behavior. The reason is that they constitute classic recursively self-amplifying collective action problems, the hallmark of which is the efficient aggregation of individually rational behaviors into collectively calamitous outcomes. In the present case, individuals rationally "legged the spread" between cheap borrowing costs and credit-fueled capital gains rates, neither of which market actors could affect in their individual capacities even when knowing that credit would have eventually to run out at some indefinite point in future. The upshot was a continuous series of self-reinforcing credit-fueled asset price rises, followed by a symmetrical series of hoarding-induced asset price drops once credit was exhausted. It is important to emphasize the rationality- and efficiency-compatability side of this story because prescribing a proper cure to our ills presupposes a proper diagnosis. The solution to a collective action problem, of course, is a collective agent. In the present context, that is a macroprudential financial regulator cognizant of her requisite role in tightening credit-money supplies when positive feedback loops emerge in asset markets.