Highlights of the Science and Life of Peter Varga (1946—2018)

Peter Varga has passed on October 27, 2018. His pioneering discoveries of chemical resolution at the atomic scale on surface alloys, atomic resolution of ultrathin alkali halides, nucleation of bcc iron in ultrathin films, and the microscopic structure of ultrathin alumina films stimulated worldwide research. In recognition of his outstanding scientific contributions, in December 2017 the Japanese Society for the Promotion of Science (JSPS) awarded him a prize for his distinguished contribution on the clarification of surface phenomena by atomic level investigations and the development of novel functional materials. This contribution highlights the life of Peter Varga as a scientist and as a person. With his elegance, his energy, his wit, and his generosity he was a close friend and role model to many of us, and showed us how to combine scientific curiosity and creativity with the lightness of being

Financial asset returns, direction-of-change forecasting, and volatility dynamics

We consider three sets of phenomena that feature prominently - and separately - in the financial economics literature: conditional mean dependence (or lack thereof) in asset returns, dependence (and hence forecastability) in asset return signs, and dependence (and hence forecastability) in asset return volatilities. We show that they are very much interrelated, and we explore the relationships in detail. Among other things, we show that: (a) Volatility dependence produces sign dependence, so long as expected returns are nonzero, so that one should expect sign dependence, given the overwhelming evidence of volatility dependence; (b) The standard finding of little or no conditional mean dependence is entirely consistent with a significant degree of sign dependence and volatility dependence; (c) Sign dependence is not likely to be found via analysis of sign autocorrelations, runs tests, or traditional market timing tests, because of the special nonlinear nature of sign dependence; (d) Sign dependence is not likely to be found in very high-frequency (e.g., daily) or very low-frequency (e.g., annual) returns; instead, it is more likely to be found at intermediate return horizons; (e) Sign dependence is very much present in actual U.S. equity returns, and its properties match closely our theoretical predictions; (f) The link between volatility forecastability and sign forecastability remains intact in conditionally non-Gaussian environments, as for example with time-varying conditional skewness and/or kurtosis

Financial Asset Returns, Direction-of-Change Forecasting, and Volatility Dynamics

We consider three sets of phenomena that feature prominently and separately in the financial economics literature: conditional mean dependence (or lack thereof) in asset returns, dependence (and hence forecastability) in asset return signs, and dependence (and hence forecastability) in asset return volatilities. We show that they are very much interrelated, and we explore the relationships in detail. Among other things, we show that: (a) Volatility dependence produces sign dependence, so long as expected returns are nonzero, so that one should expect sign dependence, given the overwhelming evidence of volatility dependence; (b) The standard finding of little or no conditional mean dependence is entirely consistent with a significant degree of sign dependence and volatility dependence; (c) Sign dependence is not likely to be found via analysis of sign autocorrelations, runs tests, or traditional market timing tests, because of the special nonlinear nature of sign dependence; (d) Sign dependence is not likely to be found in very high-frequency (e.g., daily) or very low-frequency (e.g., annual) returns; instead, it is more likely to be found at intermediate return horizons; (e) Sign dependence is very much present in actual U.S. equity returns, and its properties match closely our theoretical predictions; (f) The link between volatility forecastability and sign forecastability remains intact in conditionally non-Gaussian environments, as for example with time-varying conditional skewness and/or kurtosis.

Cointegration and long-horizon forecasting

It is widely believed that imposing cointegration on a forecasting system, if cointegration is, in fact, present, will improve long-horizon forecasts. The authors show that, contrary to this belief, at long horizons nothing is lost by ignoring cointegration when the forecasts are evaluated using standard multivariate forecast accuracy measures. In fact, simple univariate Box-Jenkins forecasts are just as accurate. The authors' results highlight a potentially important deficiency of standard forecast accuracy measures--they fail to value the maintenance of cointegrating relationships among variables--and the authors suggest alternatives that explicitly do so.Forecasting

How Relevant is Volatility Forecasting for Financial Risk Management?

It depends. If volatility fluctuates in a forecastable way, then volatility forecasts are useful for risk management; hence the interest in volatility forecastability in the risk management literature. Volatility forecastability, however, varies with horizon, and different horizons are relevant in different applications. Existing assessments are plagued by the fact that they are joint assessments of volatility forecastability and an assumed model, and the results vary not only with the horizon, but also with the model. To address this problem, we develop a model-free procedure for measuring volatility forecastability across horizons. Perhaps surprisingly, we find that volatility forecastability decays quickly with horizon. Volatility forecastability, although clearly of relevance for risk management at the very short horizons relevant for, say, trading desk management, may not be important for risk management more generally.e conclude in Section VI by discussing some limitations of our analysis, and offer some recommendations for implementation.

Optimal prediction under asymmetric loss

Prediction problems involving asymmetric loss functions arise routinely in many fields, yet the theory of optimal prediction under asymmetric loss is not well developed. We study the optimal prediction problem under general loss structures and characterize the optimal predictor. We compute it numerically in less tractable cases. A key theme is that the conditionally optimal forecast is biased under asymmetric loss and that the conditionally optimal amount of bias is time-varying in general and depends on higher-order conditional moments. Thus, for example, volatility dynamics (e.g., GARCH effects) are relevant for optimal point prediction under asymmetric loss. More generally, even for models with linear conditional-mean structure, the optimal point predictor is in general nonlinear under asymmetric loss, which provides a link with the broader nonlinear time series literature.Forecasting

STANDARDS OF NON-DISCRIMINATION IN INTERNATIONAL ECONOMIC LAW

The principle of non-discrimination constitutes a corner-stone in different fields of international economic law, notably international trade in goods and services as well as intellectual property and investment protection. While its basic rationale appears to be straightforward, the application of the different legal elements which constitute a non-discrimination obligation has proven to be most challenging. Adjudicating bodies have been applying different interpretations and standards with regard to the legal elements of ‘less favourable treatment', ‘likeness' and ‘regulatory purpose', which leads to a high fragmentation of the non-discrimination principle in international economic law. This article maps out the different theories for each of these elements on the examples of WTO law, NAFTA, bilateral investment treaties (BIT) and EU law and analyses how these theories affect the scope and liberalizing effect of the non-discrimination obligation. The article then attempts to develop a coherent factor-based application of non-discrimination rules suitable for all fields of international economic law. The article submits the theory that the elements of non-discrimination should not be applied as strict legal conditions which must be proven by a complainant, but as a range of factors which are weighed and balanced by the adjudicating bodie

Horizon Problems and Extreme Events in Financial Risk Management

Central to the ongoing development of practical financial risk management methods is recognition of the fact that asset return volatility is often forecastable. Although there is no single horizon relevant for financial risk management, most would agree that in many situations the relevant horizon is quite long, certainly longer than a few days. This fact creates some tension, because although short-horizon asset return volatility is clearly highly forecastable, much less is known about long-horizon volatility forecastability, which we examine in this paper. We begin by assessing some common model-based methods for converting short-horizon volatility into long-horizon volatility; we argue that such conversions are problematic even when done properly. Hence we develop and apply a new model-free methodology to assess the forecastability of volatility across horizons and find, surprisingly, that forecastability decays rapidly as the horizon lengthens. We conclude that for managing risk at horizons longer than a few weeks, attention given to direct estimation of extreme event probabilities may be more productive than attention given to modeling volatility dynamics, and we proceed to assess the potential of extreme value theory for estimating extreme event probabilities.

Horizon problems and extreme events in financial risk management

This paper was presented at the conference "Financial services at the crossroads: capital regulation in the twenty-first century" as part of session 3, "Issues in value-at-risk modeling and evaluation." The conference, held at the Federal Reserve Bank of New York on February 26-27, 1998, was designed to encourage a consensus between the public and private sectors on an agenda for capital regulation in the new century.Risk ; Forecasting

Standards of non-discrimination in international economic law

The principle of non-discrimination constitutes a corner-stone in different fields of international economic law, notably international trade in goods and services as well as intellectual property and investment protection. While its basic rationale appears to be straightforward, the application of the different legal elements which constitute a non-discrimination obligation has proven to be most challenging. Adjudicating bodies have been applying different interpretations and standards with regard to the legal elements of ‘less favourable treatment’, ‘likeness’ and ‘regulatory purpose’, which leads to a high fragmentation of the non-discrimination principle in international economic law. This article maps out the different theories for each of these elements on the examples of WTO law, NAFTA, bilateral investment treaties (BIT) and EU law and analyses how these theories affect the scope and liberalizing effect of the non-discrimination obligation. The article then attempts to develop a coherent factor-based application of non-discrimination rules suitable for all fields of international economic law. The article submits the theory that the elements of non-discrimination should not be applied as strict legal conditions which must be proven by a complainant, but as a range of factors which are weighed and balanced by the adjudicating bodies