Our paper addresses firm size as a driver of systematic credit risk in loans to small and medium enterprises (SMEs). Key contributions are the use of a unique data set of SME lending by over 400 German banks and relating systematic risk to the size dependence of regulatory capital requirements....

We introduce a model of the banking sector that formally incorporates a buffer function of capital. Heterogeneous banks choose their portfolio risk, bank size, and capital holdings. Banks voluntarily hold equity when the buffer effect against the risk of default outweighs the cost advantages of...