Speed Projects
Speed Projects Hier finden Sie die IWH EXplore Speed Projects chronologisch...
Zur Seite
Correlation Scenarios and Correlation Stress Testing
Natalie Packham, Fabian Wöbbeking
Journal of Economic Behavior and Organization,
January
2023
Abstract
We develop a general approach for stress testing correlations of financial asset portfolios. The correlation matrix of asset returns is specified in a parametric form, where correlations are represented as a function of risk factors, such as country and industry factors. A sparse factor structure linking assets and risk factors is built using Bayesian variable selection methods. Regular calibration yields a joint distribution of economically meaningful stress scenarios of the factors. As such, the method also lends itself as a reverse stress testing framework: using the Mahalanobis distance or Highest Density Regions (HDR) on the joint risk factor distribution allows to infer worst-case correlation scenarios. We give examples of stress tests on a large portfolio of European and North American stocks.
Artikel Lesen
The Disciplining Effect of Supervisory Scrutiny in the EU-wide Stress Test
Christoffer Kok, Carola Müller, Steven Ongena, Cosimo Pancaro
Journal of Financial Intermediation,
January
2023
Abstract
Relying on confidential supervisory data related to the 2016 EU-wide stress test, this paper presents novel empirical evidence that supervisory scrutiny associated to stress testing has a disciplining effect on bank risk. We find that banks that participated in the 2016 EU-wide stress test subsequently reduced their credit risk relative to banks that were not part of this exercise. Relying on new metrics for supervisory scrutiny that measure the quantity, potential impact, and duration of interactions between banks and supervisors during the stress test, we find that the disciplining effect is stronger for banks subject to more intrusive supervisory scrutiny during the exercise. We also find that a strong risk management culture is a prerequisite for the supervisory scrutiny to be effective. Finally, we show that a similar disciplining effect is not exerted neither by higher capital charges nor by more transparency and related market discipline induced by the stress test.
Artikel Lesen
A Factor-model Approach for Correlation Scenarios and Correlation Stress Testing
Natalie Packham, Fabian Wöbbeking
Journal of Banking and Finance,
April
2019
Abstract
In 2012, JPMorgan accumulated a USD 6.2 billion loss on a credit derivatives portfolio, the so-called “London Whale”, partly as a consequence of de-correlations of non-perfectly correlated positions that were supposed to hedge each other. Motivated by this case, we devise a factor model for correlations that allows for scenario-based stress testing of correlations. We derive a number of analytical results related to a portfolio of homogeneous assets. Using the concept of Mahalanobis distance, we show how to identify adverse scenarios of correlation risk. In addition, we demonstrate how correlation and volatility stress tests can be combined. As an example, we apply the factor-model approach to the “London Whale” portfolio and determine the value-at-risk impact from correlation changes. Since our findings are particularly relevant for large portfolios, where even small correlation changes can have a large impact, a further application would be to stress test portfolios of central counterparties, which are of systemically relevant size.
Artikel Lesen
Stress Testing and Bank Efficiency: Evidence from Europe
Iftekhar Hasan, Fotios Pasiouras
International Journal of Corporate Finance and Accounting,
Nr. 2,
2015
Abstract
This study examines whether and how the stress testing of European banks in 2010, 2011, and 2014 is related to their technical, allocative, and cost efficiency. Using a sample of large commercial banks operating in 20 European countries, and Data Envelopment Analysis (DEA), the authors perform comparisons between banks that were included in one of the three European stress tests and untested banks operating in the same countries. They estimate various specifications as for the inputs and outputs, cross-section and pooled estimations, and they also examine alternative samples as for the ownership of banks. In general, the authors conclude that banks included in the stress-test exercises are more efficient that their counterparties. The differences tend to be statistically significant in the case of allocative efficiency and cost efficiency, but not in the case of technical efficiency. With regards to the latter form of efficiency, the results depend upon the specification and the stress test in question.
Artikel Lesen
Shocks at Large Banks and Banking Sector Distress: The Banking Granular Residual
S. Blank, Claudia M. Buch, Katja Neugebauer
Journal of Financial Stability,
Nr. 4,
2009
Abstract
Size matters in banking. In this paper, we explore whether shocks originating at large banks affect the probability of distress of smaller banks and thus the stability of the banking system. Our analysis proceeds in two steps. In a first step, we follow Gabaix and construct a measure of idiosyncratic shocks at large banks, the so-called Banking Granular Residual. This measure documents the importance of size effects for the German banking system. In a second step, we incorporate this measure of idiosyncratic shocks at large banks into an integrated stress-testing model for the German banking system following De Graeve et al. (2008). We find that positive shocks at large banks reduce the probability of distress of small banks.
Artikel Lesen