Basel-2 capital adequacy: Computing the ‘fair’ capital charge for loan commitment ‘true’ credit risk

This research makes two contributions: (i) to price analytically put option and extension premium embedded in a borrower-extendible commitment, and (ii) to compute the ‘fair’ capital charge that corresponds to the commitment ‘true’ credit risk. In doing so, the procedure replaces the BIS accounting-based concepts of credit-conversion factor, principal-risk factor, and initial term to maturity of irrevocable commitments with the market-based concepts of exercise-cum-takedown proportion and put value implicit in the borrower-extendible commitment, respectively. Finally, the approach is developed one step further to account for the borrowers' risk ratings by public credit agencies; this results in a two-dimensional (time-state of nature) risk-weighting system that applies to all commitment types.