What is the optimal capital ratio implying a stable European banking system?

Abstract

This paper aims to determine the ‘new normal’ for banking stability in terms of capital adequacy, reviewing the incidence of banking stress episodes by lagged solvency ratios, based on the experience at the European level after the global financial crisis. We provide rating ladders for both risk-weighted solvency ratios and a simple gearing (leverage) ratio for time horizons of up to 3 years using well-known credit risk scoring procedures. Our findings empirically confirm that the recent dual metric structure of the capital adequacy framework is conducive to enhancing the accuracy of banking stability assessment. Specifically, our empirical analysis suggests that both tier 1 capital ratio and leverage ratio generally remain statistically significant in multivariate combinations for crisis probability measurement purposes. Robustness checks with well-established macrofinancial indicators as control variables suggest that this tandem is hardly replaceable in multivariate early warning systems by combinations of macroimbalance and financial soundness indicators traditionally employed as leading factors of banking crises. Moreover, the pandemic period provides meaningful evidence that robust capital positions, in line with our estimate, have so far been ‘part of the solution’ for dealing with systemic events.