Professor of Finance
Chair in Sustainable Finance & Banking
Email: weiss -at- wifa.uni-leipzig.de
Phone: +49 341 97 33821
Fax: +49 341 97 33829
Marginals Versus Copulas: Which Account For More Model Risk In Multivariate Risk Forecasting?, with Simon Fritzsch and Maike Timphus.
Copulas. We study the model risk of multivariate risk models using a comprehensive empirical study on Copula-GARCH models used for forecasting Value-at-Risk and Expected Shortfall. To determine whether model risk inherent in the forecasting of portfolio risk is caused by the candidate marginal or copula models, we analyze different groups of models in which we fix either the marginals, the copula, or neither. Model risk is economically significant, is especially high during periods of crisis, and is almost completely due to the choice of the copula. We then propose the use of the model confidence set procedure to narrow down the set of available models and reduce model risk for Copula-GARCH risk models. Our proposed approach leads to a significant improvement in the mean absolute deviation of one day ahead forecasts by our various candidate risk models.
with Simon Fritzsch and Philipp Scharner, Journal of Risk and Insurance, forthcoming.
We analyze the relation between digitalization and the market value of US insurance companies. To create a text-based measure that captures the extent to which insurers digitalize, we apply an unsupervised machine learning algorithm - Latent Dirichlet Allocation - to their annual reports. We show that an increase in digitalization is associated with an increase in market valuations in the insurance sector. In detail, capital market participants seem to reward digitalization efforts of an insurer in the form of higher absolute market capitalizations and market-to-book ratios. Additionally, we provide evidence that the positive relation between digitalization and market valuations is robust to sentiment in the annual reports and the choice of the reference document on digitalization, both being issues of particular importance in text-based analyses.
with Simon Fritzsch and Felix Irresberger
This paper presents a robust new finding that delta-hedged equity option returns include a volatility risk premium. To separate volatility risk premia from confounding effects, we estimate conditional quantile curves of implied volatilities using machine learning. We find that a zero-cost trading strategy that is long (short) in the portfolio with low (high) implied volatility conditional on the options' moneyness and realized volatility produces an economically and statistically significant average monthly return. Using conditional quantile curves not only helps in distinguishing volatility risk premia from other effects, most notably realized volatility, it also leads to returns that are higher than those reported in previous work on similar volatility strategies.