Low Interest Rates and Banks’ Interest Margins: Does Deposit Market Concentration Matter?

Using a sample of 7,919 banks from 30 OECD countries over 1995–2019, we examine the impact of low interest rates on banks’ net interest margins. Our results confirm a positive relationship between interest rates and interest margins, which is stronger in a low interest rate environment. In more concentrated markets, however, interest margins are less sensitive to the level of interest rates, as interest rate sensitivities of income and expense margins match. But our results also suggest that the effect of market concentration on the link between interest rates and interest margins is weaker when interest rates approach zero.