Novel three-bank model for measuring the systemic importance of commercial banks

Relaxing the hypothesis on the scale level of a bank, the present paper develops an improved three-bank model for analyzing the relationship between the size and the systemic importance of a bank. The proposed model is more general and more operational compared with other models. By introducing the L function based on the multivariate extreme theory and the systemically important index, the effect of the size on the systemic importance of a bank is analyzed. The size is found to be a necessary but insufficient condition for measuring the systemic importance of a bank. The size of a bank plays a critical role in evaluating systemic importance, but when the size reaches a certain threshold, its effect is weakened. The current study has theoretical and practical significance for the recognition and supervision of the systemic importance of banks.