The paper develops a new approach to measuring variability in banks' risk-weighted assets (RWAs), which compares a market-implied estimate of a bank's risk profile with the bank's own estimate. This variability ratio provides an external benchmark to assess the degree of difference in modelled capital requirements across banks and over time.
It also provides a quantitative measure to assess the extent to which this difference has narrowed as a result of the Basel III reforms.
The pre-crisis regulatory framework provided banks with a large degree of discretion in determining their capital requirements. This resulted in excessive variability in banks' capital requirements, which ultimately undermined the credibility of the risk-weighted capital framework at the peak of the global financial crisis. The Basel III post-crisis reforms developed by the Basel Committee seek to reduce this variability. How successful will they be in achieving this outcome?
Over the period 2001 to 16, there was a wide degree of RWA variability among banks. Market-implied RWA estimates were higher than those modelled by banks.
What drove this variability? Authors find a significant association between the degree of RWA variability and:
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the share of opaque assets held by banks (eg derivatives);
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the degree to which a bank is constrained by its capital requirements; and
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jurisdiction-specific factors.
Put differently, market participants 'penalise' banks with such features relative to other banks.
And regarding Basel III - authors find that the 2017 Basel III reforms - most notably the output floor - help to reduce excessive RWA variability.
Full working paper on BIS
© BIS - Bank for International Settlements
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