1. University of Leuven, Hogenheuvelcollege, Naamsestraat 69, 3000 Leuven, Belgium; and UNU-MERIT and Maastricht University
2. The European Commission, Joint Research Centre TP 361, Via E. Fermi 2749, 21027 Ispra (VA), Italy
3. University of Leuven, Hogenheuvelcollege, Naamsestraat 69, 3000 Leuven, Belgium; and Vlerick Business School
4. University of Leuven, ECOOM, Waaistraat 6, bus 3536, 3000 Leuven, Belgium