A Top-down Approach to Stress-testing Banks

Abstract

We propose a simple, parsimonious, and easily implementable method for stress-testing banks using a top-down approach that captures the heterogeneous impact of shocks to macroeconomic variables on banks’ capitalization. Our approach relies on a variable selection method to identify the macroeconomic drivers of banking variables as well as the balance sheet and income statement factors that are key in explaining bank heterogeneity in response to macroeconomic shocks. We perform a principal component analysis on the selected variables and show how the principal component factors can be used to make projections, conditional on exogenous paths of macroeconomic variables. We apply our approach, using alternative estimation strategies and assumptions, to the 2013 and 2014 stress tests of medium- and large-size U.S. banks mandated by the Dodd-Frank Act, and obtain stress projections for capitalization measures at the bank-by-bank and industry-wide levels. Our results suggest that accounting for bank heterogeneity yields expected capital shortfalls that can be over 30 percent larger than in the case where heterogeneity is ignored. Furthermore, we find that while capitalization of the U.S. banking industry has improved in recent years, under reasonable assumptions regarding growth in assets and loans, the stress scenarios continue to imply sizable deterioration in banks’ capital positions.