An evaluation of the Basel III market risk proposals
28 November 2013
The Basel committee has proposed significant changes in the way market risk is forecasted. These pages provide some quantitative analysis of those proposals and accompany the VoxEU article « An evaluation of the Basel III market risk proposals on 28 November 2013.
An updated version of the analysis is here.
Tables and plots
Summary of the results
The Basel Committee has proposed for significant changes to how market risk is forecasted
The original 1996 version of the market risk regulations, essentially still in effect, are about to see significant changes, in particular:
- a move to expected shortfall (ES) from Value-at-Risk (VaR);
- lowering of the confidence level from 99% to 97.5%;
- the holding period is calculated by overlapping windows;
- ES is to be adjusted by stressed observations.
The results show that there is little difference between 99% VaR and 97.5% ES. In the conditional Gaussian case they are essentially the same, and since such a model is probably the most common in industry, this seems to be no gain to be had from moving to ES. For fat tailed conditional distributions, ES 97.% Is slightly higher than 99% VaR but by a factor of 10% or less, so the impact seems to be minimal.
However, the ES results are more volatile, so by making the switch, the magnitude of the risk forecast is essentially the same, but the uncertainty it higher.
The move to overlapping holding periods seems to provide biased risk forecasts, and significantly increasing forecast uncertainty, in some cases so large that the actual forecast is statistically insignificantly different from zero.