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Ein Value-at-Risk-Limit wird als DM-Betrag gekennzeichnet, der von den tatsächlichen Handelsverlusten innerhalb einer bestimmten Zeitdauer nur mit geringer Wahrscheinlichkeit überschritten werden darf. Da der Bankvorstand i.d.R. Jahres-Value-at-Risk-Limite beschließt, im Handelsbereich die Geschäfte aber für einen kurzfristigen - unterstellt wird ein eintägiger - Planungshorizont abgeschlossen werden, ist zu klären, wie Jahres-Limite in Tages-Limite umgerechnet und während des Jahres realisierte Gewinne und Verluste auf die Limite angerechnet werden können. Auf der Grundlage des Umrechnungsverfahrens nach der Quadratwurzel-T-Formel lassen sich drei Verfahren für die Ermittlung des Tages-Limits unterscheiden: 1. Realisierte Gewinne und Verluste werden nicht angerechnet (starres Limit). 2. Bei Verlusteintritt vermindert sich das Tages-Limit für die Restperiode, realisierte Gewinne machen Kürzungen rückgängig (Verlustbegrenzungslimit). 3. Tages-Limite werden um Gewinne und Verluste angepaßt, wodurch eine Erweiterung des Handlungsspielraumes möglich ist (dynamisches Limit). Die drei Limite werden in einem Simulationsmodell gegeneinander abgewogen, wobei unterstellt wird, ein Händler handle nur eine einzige Aktie und antizipiere in 55% der Fälle die Kursrichtung. Die Simulationsergebnisse sind bei den unterstellten Renditeprozessen (geometrische Brownsche Bewegung und reale Renditen von 77 deutschen Aktien für die Zeit vom 01.01.1974 bis 31.12.1995) weitgehend identisch. Das dynamische Limit produziert deutlich höhere durchschnittliche Ergebnisse als das starre Limit und das Verlustbegrenzungslimit. Überschreitungen des Jahres-Limits treten nur beim starren Verfahren auf, die Häufigkeit ist allerdings wesentlich geringer als die zulässige Wahrscheinlichkeit von 1 %.
We show that the use of correlations for modeling dependencies may lead to counterintuitive behavior of risk measures, such as Value-at-Risk (VaR) and Expected Short- fall (ES), when the risk of very rare events is assessed via Monte-Carlo techniques. The phenomenon is demonstrated for mixture models adapted from credit risk analysis as well as for common Poisson-shock models used in reliability theory. An obvious implication of this finding pertains to the analysis of operational risk. The alleged incentive suggested by the New Basel Capital Accord (Basel II), amely decreasing minimum capital requirements by allowing for less than perfect correlation, may not necessarily be attainable.
This study analyzes the short-term dynamic spillovers between the futures returns on the DAX, the DJ Eurostoxx 50 and the FTSE 100. It also examines whether economic news is one source of international stock return co-movements. In particular, we test whether stock market interdependencies are attributable to reactions of foreign traders to public economic information. Moreover, we analyze whether cross-market linkages remain the same or whether they do increase during periods in which economic news is released in one of the countries. Our main results can be summarized as follows: (i) there are clear short term international dynamic interactions among the European stock futures markets; (ii) foreign economic news affects domestic returns; (iii) futures returns adjust to news immediately; (iv) announcement timing of macroeconomic news matters; (v) stock market dynamic interactions do not increase at the time of the release of economic news; (vi) foreign investors react to the content of the news itself more than to the response of the domestic market to the national news; and (vii) contemporaneous correlation between futures returns changes at the time of macroeconomic releases. JEL Classification: G14, G15
This paper discusses the role of the credit rating agencies during the recent financial crises. In particular, it examines whether the agencies can add to the dynamics of emerging market crises. Academics and investors often argue that sovereign credit ratings are responsible for pronounced boom-bust cycles in emerging-markets lending. Using a vector autoregressive system this paper examines how US dollar bond yield spreads and the short-term international liquidity position react to an unexpected sovereign credit rating change. Contrary to common belief and previous studies, the empirical results suggest that an abrupt downgrade does not necessarily intensify a financial crisis.
We examine intra-day market reactions to news in stock-specific sentiment disclosures. Using pre-processed data from an automated news analytics tool based on linguistic pattern recognition we extract information on the relevance as well as the direction of company-specific news. Information-implied reactions in returns, volatility as well as liquidity demand and supply are quantified by a high-frequency VAR model using 20 second intervals. Analyzing a cross-section of stocks traded at the London Stock Exchange (LSE), we find market-wide robust news-dependent responses in volatility and trading volume. However, this is only true if news items are classified as highly relevant. Liquidity supply reacts less distinctly due to a stronger influence of idiosyncratic noise. Furthermore, evidence for abnormal highfrequency returns after news in sentiments is shown. JEL-Classification: G14, C32
The use of GARCH models with stable Paretian innovations in financial modeling has been recently suggested in the literature. This class of processes is attractive because it allows for conditional skewness and leptokurtosis of financial returns without ruling out normality. This contribution illustrates their usefulness in predicting the downside risk of financial assets in the context of modeling foreign exchange-rates and demonstrates their superiority over use of normal or Student´s t GARCH models.
Gauging risk with higher moments : handrails in measuring and optimising conditional value at risk
(2009)
The aim of the paper is to study empirically the influence of higher moments of the return distribution on conditional value at risk (CVaR). To be more exact, we attempt to reveal the extent to which the risk given by CVaR can be estimated when relying on the mean, standard deviation, skewness and kurtosis. Furthermore, it is intended to study how this relationship can be utilised in portfolio optimisation. First, based on a database of 600 individual equity returns from 22 emerging world markets, factor models incorporating the first four moments of the return distribution have been constructed at different confidence levels for CVaR, and the contribution of the identified factors in explaining CVaR was determined. Following this the influence of higher moments was examined in portfolio context, i.e. asset allocation decisions were simulated by creating emerging market portfolios from the viewpoint of US investors. This can be regarded as a normal decisionmaking process of a hedge fund focusing on investments into emerging markets. In our analysis we compared and contrasted two approaches with which one can overcome the shortcomings of the variance as a risk measure. First of all, we solved in the presence of conflicting higher moment preferences a multi-objective portfolio optimisation problem for different sets of preferences. In addition, portfolio optimisation was performed in the mean-CVaR framework characterised by using CVaR as a measure of risk. As a part of the analysis, the pair-wise comparison of the different higher moment metrics of the meanvariance and the mean-CVaR efficient portfolios were also made. Throughout the work special attention was given to implied preferences to the different higher moments in optimising CVaR. We also examined the extent to which model risk, namely the risk of wrongly assuming normally-distributed returns can deteriorate our optimal portfolio choice. JEL Classification: G11, G15, C61
We present an analysis of VaR forecasts and P&L-series of all 13 German banks that used internal models for regulatory purposes in the year 2001. To this end, we introduce the notion of well-behaved forecast systems. Furthermore, we provide a series of statistical tools to perform our analyses. The results shed light on the forecast quality of VaR models of the individual banks, the regulator's portfolio as a whole, and the main ingredients of the computation of the regulatory capital required by the Basel rules.
Ensuring financial stability : financial structure and the impact of monetary policy on asset prices
(2008)
This paper studies the responses of residential property and equity prices, inflation and economic activity to monetary policy shocks in 17 countries, using data spanning 1986-2006. We estimate VARs for individual economies and panel VARs in which we distinguish between groups of countries on the basis of the characteristics of their financial systems. The results suggest that using monetary policy to offset asset price movements in order to guard against financial instability may have large effects on economic activity. Furthermore, while financial structure influences the impact of policy on asset prices, its importance appears limited. Keywords: asset prices, monetary policy, panel VAR. JEL Number: C23, E52
A resampling method based on the bootstrap and a bias-correction step is developed for improving the Value-at-Risk (VaR) forecasting ability of the normal-GARCH model. Compared to the use of more sophisticated GARCH models, the new method is fast, easy to implement, numerically reliable, and, except for having to choose a window length L for the bias-correction step, fully data driven. The results for several different financial asset returns over a long out-of-sample forecasting period, as well as use of simulated data, strongly support use of the new method, and the performance is not sensitive to the choice of L. Klassifizierung: C22, C53, C63, G12