Expected Shortfall Reliability—Added Value of Traditional Statistics and Advanced Artificial Intelligence for Market Risk Measurement Purposes

The Fundamental Review of the Trading Book is a market risk measurement and management regulation recently issued by the Basel Committee. This reform, often referred to as “Basel IV”, intends to strengthen the financial system. The newest capital standard relies on the use of the Expected Shortfall. This risk measure requires to get sufficient information in the tails to ensure its reliability, as this one has to be alimented by a sufficient quantity of relevant data (above the 97.5 percentile in the case of the regulation or interest). In this paper, after discussing the relevant features of Expected Shortfall for risk measurement purposes, we present and compare several methods allowing to ensure the reliability of the risk measure by generating information in the tails. We discuss these approaches with respect to their relevance considering the underlying situation when it comes to available data, allowing practitioners to select the most appropriate approach. We apply traditional statistical methodologies, for instance distribution fitting, kernel density estimation, Gaussian mixtures and conditional fitting by Expectation-Maximisation as well as AI related strategies, for instance a Synthetic Minority Over-sampling Technique implemented in a regression environment and Generative Adversarial Nets.

Capital regulations, supervision and the international harmonization of bank capital ratios

In recent decades, despite the Basel Committee’s effort to develop internationally uniform regulatory capital standards, the capital ratios of banks across countries continue to exhibit significant differences. This paper examines the fundamental question of whether, given a uniform regulatory capital standard, regulators should expect similar banks to exhibit similar risk-based capital ratios. More specifically, this study develops a one-period theoretical model to examine the level playing field argument in light of not only uniform regulatory capital standards but also differences in bank supervision. The results of the theoretical model suggest that even with an internationally uniform risk-based capital requirement, it is unreasonable to expect banks in different countries to hold similar capital ratios. This occurs, in part, because regulators have discretion in how they apply the risk-based capital standards. Furthermore, the results suggest that a necessary condition for banks to exhibit similar capital ratios is that uniform capital requirements must be accompanied by a uniform stringency and application of regulatory supervision.