Economies of superscale in commercial banking

Most previous studies of scale economies in banking have excluded banks larger than $1 billion in assets. Thus study, by contrast, estimates cost functions for the 100 largest US commercial banks. ‘Hedonic’ terms are incorporated to correct for the aggregated nature of the Call Report data available for these banks. In addition, we attempt to quantify the cost benefit of diversification in the model. We estimate efficient bank scale to range from $15 billion to $37 billion in total assets, a thousandfold increase over some previous findings. These results are supported by comparison of actual average costs, as well as by casual historical observation and the level of widespread concern over interstate banking. Our findings suggest some cost incentive or benefit to expansion or consolidation among large regional banks, including interstate expansion or consolidation.