Foundations of system-wide financial stress testing with heterogeneous institutions

We propose a structural framework for the development of system-wide financial stress tests with multiple interacting contagion, amplification channels and heterogeneous financial institutions. This framework conceptualises financial systems through the lens of five building blocks: financial institutions, contracts, markets, constraints, and behaviour. Using this framework, we implement a system-wide stress test for the European financial system. We obtain three key findings. First, the financial system may be stable or unstable for a given microprudential stress test outcome, depending on the system's shock-amplifying tendency. Second, the 'usability' of banks' capital buffers (the willingness of banks to use buffers to absorb losses) is of great consequence to systemic resilience. Third, there is a risk that the size of capital buffers needed to limit systemic risk could be severely underestimated if calibrated in the absence of system-wide approaches.