Lean IRB Approaches and Transition Design : The Basel Ii Proposal

The internal ratings based approach (IRB) of the Basel Committee has three problems: few incentives for banks to adopt the IRB approach, a complicated technical framework and very conservative aggregation rules. We suggest the following remedies: First, we suggest a new design of transition rules that produce strong incentives for banks to adopt the IRB approach. Second, we outline a lean IRB approach which is simpler and avoids adjustments and caps that are difficult to justify. This approach can be flexibly calibrated to proxy any IRB approach. Third, we suggest a simple aggregation rule for capital requirements across portfolio segments that takes the diversification effect across segments into account