31 January 2013
The Basel Committee on Banking Supervision has today published its report on the regulatory consistency of risk-weighted assets for market risk. This analysis of risk-weighted assets in the trading book is part of the wider Regulatory Consistency Assessment Programme (RCAP) initiated by the Committee in 2012; a similar analysis is currently under way for the banking book. The programme aims to ensure consistent implementation of the Basel framework, which will help strengthen the resilience of the global banking system, maintain market confidence in regulatory ratios and provide a level playing field for banks operating internationally.
The report brings together two pieces of analysis. The first is based on an examination of publicly available bank data for a selection of large banks. It also contains the results of a hypothetical test portfolio exercise, in which 15 internationally active banks participated.
The report presents preliminary estimates of variation in risk-weighted assets for market risk (mRWAs) across banks and highlights aspects of the Basel standards that contribute to that variation. Based on publicly available reports, the analysis shows considerable variation in average published mRWAs. While there was some indication from the public data that differences in the composition and size of trading positions are correlated with banks' average mRWAs, the quality of disclosures was found to be insufficient to allow investors and other interested parties to assess how much of the variation reflects differing levels of actual risk and how much is a result of other factors.
The hypothetical test portfolio exercise indicated that, based on the use of a hypothetical diversified portfolio consisting primarily of simple long and short positions, there can be a substantial difference between the bank reporting the lowest mRWAs and the bank reporting the highest. This range of outcomes is attributed to a number of factors:
While hypothetical test portfolios can overcome the limitations encountered when attempting to use public and supervisory data - as they control for differences in portfolio composition - they only show potential and not realised variation in outcome. Moreover, in this case the exercise focused not on real-life portfolio outcomes but rather on a series of simple long and short positions, designed to reveal the impact of model design features. To shed more light on the effect of different sources of variation on more realistic portfolios, the Basel Committee plans to conduct a further hypothetical test portfolio exercise later this year. This will include other, more complex, hypothetical test portfolios, with the aim of helping the Committee to deepen its analysis of the variation in risk measurement of trading books across banks.
Commenting on the report, Stefan Ingves, Chairman of the Basel Committee and Governor of Sveriges Riksbank, said: "While some variation in risk weightings should be expected, excessive variation arising from bank modelling choices is undesirable when it does not reflect actual risk-taking. These preliminary findings will feed into the policy work already initiated by the Basel Committee, in particular regarding the enhancement of bank disclosures and the fundamental review of the trading book. Also, the analysis used to compile this report provides national supervisors with a much clearer understanding of how the risk models of their banks compare with those of international peers. This will allow national supervisors to take action where needed."