Concentration risk is an important feature of many banking sectors, especially in emerging and
small economies. Under the Basel Framework, Pillar 1 capital requirements for credit risk do not
cover concentration risk, and those calculated under the Internal Ratings Based (IRB) approach
explicitly exclude it. Banks are expected to compensate for this by autonomously estimating and
setting aside appropriate capital buffers, which supervisors are required to assess and possibly
challenge within the Pillar 2 process. Inadequate reflection of this risk can lead to insufficient
capital levels even when the capital ratios seem high. We propose a flexible technique, based on
a combination of “full” credit portfolio modeling and asymptotic results, to calculate capital
requirements for name and sector concentration risk in banks’ portfolios. The proposed approach
lends itself to be used in bilateral surveillance, as a potential area for technical assistance on
banking supervision, and as a policy tool to gauge the degree of concentration risk in different
banking systems.