Bank diversification and performance: Empirical evidence from Japan

This article examines the relationship between bank diversification and performance in the Japanese banking sector. We use panel data from 141 banks over the period 2000-2022 to investigate whether banks can improve profitability and reduce risk through diversification strategies. Our evidence shows that diversification can improve bank profitability at the cost of a decline in net interest margins, suggesting banks are using the interest business as a loss leader to promote other business lines. We find that asset diversification has a risk-reducing effect, which supports the portfolio hypothesis. Some evidence also implies that there is a more complex nonlinear relationship. This can be partly attributed to bank type, as the diversification effects vary across different types of banks. Furthermore, the decomposition of non-interest income reveals that fees and commissions negatively influence return on assets while simultaneously reducing bank risk.