A previous version of this working paper was originally published in July 2011.

The authors investigate whether large size provides any cost advantages to the economy and, if so, whether these cost advantages are due to technological scale economies or too-big-to-fail subsidies. Estimating scale economies is made more complex by risk-taking. Better diversification resulting from larger scale generates scale economies but also incentives to take more risk. When this additional risk-taking adds to cost, it can obscure the underlying scale economies and engender misleading econometric estimates of them. Using data pre- and post-crisis, they estimate scale economies using two production models. The standard model ignores endogenous risk-taking and finds little evidence of scale economies. The model accounting for managerial risk preferences and endogenous risk-taking finds large scale economies, which are not driven by too-big-to-fail considerations. The authors evaluate the costs and competitive implications of breaking up the largest banks into smaller banks.