Estimation Uncertainty in Credit Risk Assessment: Comparison of Credit Risk Using Bootstrapping and an Asymptotic Approach
Henry Dannenberg
IWH Discussion Papers,
No. 3,
2009
Abstract
Bei der Kreditrisikobewertung müssen die Parameter Ausfallwahrscheinlichkeit und
-korrelation geschätzt werden. Diese Schätzung erfolgt unter Unsicherheit. In der Literatur werden asymptotische Konfidenzregionen diskutiert, um diese Unsicherheit bei der simultanen Schätzung beider Parameter zu bewerten. Diese Regionen setzen allerdings eine sehr lange Datenhistorie für eine genaue Bewertung voraus. Als Alternative bietet sich bei kurzen Datenhistorien Bootstrapping an. Diese Methode ist allerdings deutlich rechenintensiver. Im vorliegenden Beitrag wird untersucht, ab welcher Anzahl historisch verfügbarer Perioden Bootstrapping und eine Wald-Konfidenzregion zu einer vergleichbaren Bewertung des Kreditrisikos gelangen. Die hier genutzten Methoden führen zu ähnlichen Ergebnissen, wenn über 100 historische Perioden zur Verfügung stehen.
Read article
Exploring the International Linkages of the Euro Area: A Global VAR Analysis
Stéphane Dées, Filippo di Mauro, M. Hashem Pesaran, Vanessa Smith
Journal of Applied Econometrics,
No. 1,
2007
Abstract
Abstract This paper presents a quarterly global model combining individual country vector error-correcting models in which the domestic variables are related to the country-specific foreign variables. The global VAR (GVAR) model is estimated for 26 countries, the euro area being treated as a single economy, over the period 1979?2003. It advances research in this area in a number of directions. In particular, it provides a theoretical framework where the GVAR is derived as an approximation to a global unobserved common factor model. Using average pair-wise cross-section error correlations, the GVAR approach is shown to be quite effective in dealing with the common factor interdependencies and international co-movements of business cycles. It develops a sieve bootstrap procedure for simulation of the GVAR as a whole, which is then used in testing the structural stability of the parameters, and for establishing bootstrap confidence bounds for the impulse responses. Finally, in addition to generalized impulse responses, the current paper considers the use of the GVAR for ?structural? impulse response analysis with focus on external shocks for the euro area economy, particularly in response to shocks to the US.
Read article
Economies of Scope in European Railways: An Efficiency Analysis
Christian Growitsch, Heike Wetzel
IWH Discussion Papers,
No. 5,
2006
Abstract
In the course of railway reforms in the end of the last century, national European governments, as well the EU Commission, decided to open markets and to separate railway networks from train operations. Vertically integrated railway companies – companies owning a network and providing transport services – argue that such a separation of infrastructure and operations would diminish the advantages of vertical integration and would therefore not be suitable to raise economic welfare. In this paper, we conduct a pan-European analysis to investigate the performance of European railways with a particular focus on economies of vertical integration. We test the hypothesis that integrated railways realise economies of joint production and, thus, produce railway services on a higher level of efficiency. To determine whether joint or separate production is more efficient we apply a Data Envelopment Analysis super-efficiency bootstrapping model which relates the efficiency for integrated production to a virtual reference set consisting of the separated production technology. Our findings are that in a majority of European Railway companies exist economies of scope.
Read article
