The benefits and costs of geographic diversification in banking

We estimate the benefits of geographic diversification within states and across states for bank risk and return for all U.S. bank holding companies from 1994 to 2008, and assess whether such benefits depend on bank size. For small banks, only intrastate diversification increases risk-adjusted returns and reduces default risk while for very large institutions only interstate expansions are beneficial but only in terms of default risk. In all cases the relationship is hump-shaped indicating that at some point, the possible agency costs associated with banks getting wider and more geographically diversified outweigh the benefits. Our results indicate that small banks and very large banks could still benefit from further geographic diversification.