Bank Interest Margin and Default Risk under the Capped Schedule for Government Capital Injections in the Basel III Capital Adequacy Accord

The Basel III Capital Adequacy Accord (BCAA) will cap government capital injections as qualifying capital at 90% of the nominal amount of such capital outstanding, beginning in 2013, and the cap will decline by 10% during each subsequent year (Eubanks, 2010); this cap is called a capped ratio schedule of government capital instruments. We add to the literature on government capital injections by providing an option-based illustration of how the capped ratio schedule can influence bank interest margins and failure probability. We show that a declining capped ratio increases a bank’s volume of lending at a reduced margin and further increases its default risk. The capped ratio schedule as such makes the bank less prudent and more prone to risk-taking, thereby adversely affecting the stability of the banking system. Our findings provide alternative explanations for criticisms of BCAA.