Fat tails,VaR and subadditivity

Financial institutions rely heavily on Value-at-Risk (VaR) as a risk measure, even though it is not globally subadditive. First, we theoretically show that the VaR portfolio measure is subadditive in the relevant tail region if asset returns are multivariate regularly varying, thus allowing for dependent returns. Second, we note that VaR estimated from historical simulations may lead to violations of subadditivity. This upset of the theoretical VaR subadditivity in the tail arises because the coarseness of the empirical distribution can affect the apparent fatness of the tails. Finally, we document a dramatic reduction in the frequency of subadditivity violations, by using semi-parametric extreme value techniques for VaR estimation instead of historical simulations.     

Does quality influence choice of general practitioner? An analysis of matched doctor–patient panel data

The impact of quality on the demand facing health care providers has important implications for the industrial organization of health care markets. In this paper we study the consumers' choice of general practitioner (GP), assuming they are unable to observe the true quality of GP services. A panel data set for 484 Norwegian GPs, with summary information on their patient stocks, renders the opportunity to identify and measure the impact of GP quality on the demand, accounting for patient health heterogeneity. We apply a multi-equation model in the LISREL format, with GP quality and patient health as latent determinants of demand for GP services. Patient excess mortality rate at the GP level is one indicator of quality. Our results indicate that GP quality has a clear positive effect on demand, even when patient heterogeneity is accounted for.     

Recursions for Distribution Functions and Stop-Loss Transforms

For any function f on the non-negative integers, we can evaluate the cumulative function o f given by o f ( s )= ~ s x=0 f ( x ) from the values of f by the recursion o f ( s )= o f ( s -1)+ f ( s ). Analogously we can use this procedure t times to evaluate the t -th order cumulative function o t f . As an alternative, in the present paper we shall derive recursions for direct evaluation of o t f when f itself satisfies a certain sort of recursion. We shall also derive recursions for the t -th order tails v t f where v f ( s )= ~ X x=s+1 f ( x ). The recursions can be applied for exact and approximate evaluation of distribution functions and stop-loss transforms of probability distributions. The class of recursions for f includes the classes discussed by Sundt (1992), incorporating the class studied by Panjer's (1981). We discuss in particular convolutions and compound functions.     

In the eyes of the beholder: the HRM capabilities of the HR function as perceived by managers and professionals

This study investigated factors influencing line managers' and professionals' perceptions of the HRM capabilities of the HR function. Using a sample of 913 managers and professionals in subsidiaries of 11 Nordic multinational corporations, we tested the extent to which features of the unit's HRM system, attitudes of the unit's general manager and characteristics of the HR manager helped explain the perceived HRM capabilities. The analysis revealed that perceived HRM practice visibility and HRM inducements (the link between individual performance and HRM‐related benefits) were strong predictors of individual perceptions of the HR function's HRM capabilities. The use of e‐HRM and the most senior manager's attitudes towards the unit's HRM practices were also significantly related to perceived HRM capabilities.     

Using survey data to study capitalization of local public services

We use surveys in which respondents evaluate local amenities in Norway to compute proxy variables for the quality of local public services as well as other local amenities relevant to location decisions. Average satisfaction reported by the respondents is computed for each amenity and each municipality, adjusted for sample variation in personal characteristics and included as explanatory variables in a cross-section study of house prices. We find that house prices are increasing in satisfaction with cultural activities, health care, care for the elderly and public transportation.     

The natural rate of interest and the output gap in the euro area: a joint estimation

The notion of a natural real rate of interest, due to Wicksell (Interest and prices. Macmillan, London Translation of 1898 edition, 1936), is widely used in current central bank research. The idea is that there exists a level at which the real interest rate would be compatible with output at its potential level and stationary inflation. Such a concept is of primary concern for monetary policy because it provides a benchmark for the monetary policy stance. This paper applies the method suggested by Laubach and Williams (Rev Econ Stat 85(4):1063–1070, 2003) to jointly estimate the natural real interest rate and the output gap in the euro area using data from 1960 onwards. Our results suggest that the natural real rate of interest has declined gradually over the past 40 years. They also indicate that monetary policy in the euro area was on average stimulative during the 1960s and the 1970s, while it contributed to dampen the output gap and inflation in the 1980s and 1990s. The views expressed in this paper are those of the authors and do not necessarily reflect the opinions of the institutions to which they are affiliated. We are grateful to Siem Jan Koopman for very helpful suggestions and comments. We also thank P. Cour-Thimann, V. Curdia, F. Drudi, S. McCaw, D. Rodriguez-Palenzuela, R. Pilegaard, H. Pill, L. Stracca, T. Laubach, J. C. Williams and the participants of an ECB workshop on natural interest rates.     

A problem-adjusted genetic algorithm for flexibility design

Many present markets for goods and services have highly volatile demand due to short life cycles and strong competition in saturated environments. Determination of capacity levels is difficult because capacities often need to be set long before demand realizes. In order to avoid capacity-demand mismatches, operations managers employ mix-flexible resources which allow them to shift excess demands to unused capacities. The Flexibility Design Problem (FDP) models the decision on the optimal configuration of a flexible (manufacturing) network. FDP is a difficult stochastic optimization problem, for which traditional exact approaches are not able to solve but the smallest instances in reasonable time. We develop a Flexibility Design Genetic Algorithm (FGA) that exploits qualitative insights into the structure of good solutions, such as the well-established chaining principle, to enhance its performance. FGA is compared to a commercial solver, a simple GA, and a Simulated Annealing local search on instances of up to 15 demand types and resources. Experimental evidence shows that the proposed approach outperforms the competing methods with respect to both computing time and solution quality.