The determinants of bank margins revisited: A note on the effects of diversification

Most of the theoretical and empirical literature on bank margins has dealt solely with interest margins. Applying the seminal Ho-Saunders model (JFQA, 1981) to a multi-output framework, we show that the relationship between bank margins and market power (controlling for risk) varies significantly across bank specializations. Using a set of both accounting margins and New Empirical Industrial Organization (NEIO) margins, we find that market power rises significantly with output diversification towards non-traditional activities. These results contribute to explain the paradoxical coexistence of decreasing interest margins and higher market power found in previous studies.