Banking Industry Dynamics and Size-Dependent Capital Regulation
Abstract
This paper develops a model of a dynamic and heterogeneous banking sector,embedded in a general equilibrium framework. The objective is two-fold. The first is
to offer a model of the banking industry where leverage is a driver of the dynamics,
and where the implied distribution of bank capital closely matches the one that
observed in data. The second objective is to characterize the optimal size-dependent
capital regulation. The rationale for regulation arises because deposit insurance
induces banks to assume more leverage – defined as the ratio of assets to capital – than
what is socially optimal. As such, a limit on leverage improves welfare. Crucially,
the optimal regulation is size-specific – it tighter for larger banks. Intuitively, this
is for three reasons. First, allowing small banks to assume more leverage enables
them to grow faster, leading to a growth effect. Second, although more leverage by
small banks results in a higher failure rate among them, the failing banks are the less
productive ones, leading to a cleansing effect. Third, relative to small banks, large
banks entail more correlated shocks per unit asset, and are therefore, riskier. As
such, tighter regulation for large banks lowers the overall riskiness of banks’ assets,
leading to a stabilization effect. The model provides support for policies – such as the
GSIB framework – that impose tighter regulation on large and systemically important
banks.