Why is credit-to-GDP a good measure for setting countercyclical capital buffers?

We examine banks’ loan losses in Europe in 1982–2012 using a nonlinear three-factor model that takes into account output growth, real interest rate, and the ratio of private credit to GDP relative to its trend (i.e., “excessive indebtedness”). We find that a drop in output has an intensified impact on loan losses if the private sector is excessively indebted. Because increased bank credit risk should be matched with higher bank capital, the result motivates the Basel III's countercyclical capital buffers as a function of private indebtedness relative to its trend. The result also helps to explain differences in the amount of loan losses in different recessions across time and across countries. The model also indicates that low interest rates during the recent recession have clearly mitigated loan losses.