1. Department of Statistics TU Dortmund, Vogelpothsweg 78 Dortmund Germany
2. Faculty of Economics and Business Administration University of Duisburg‐Essen, Universitätsstraße 12 Essen Germany
3. Faculty of Economics University of Hagen, Universitätsstraße 41 Hagen Germany
4. CREATES Aarhus University, School of Economics and Management, Fuglesangs Allé 4 Aarhus V Denmark