1. Research Assistant, Dept. of Management Information Science and Operations Management, Faculty of Economics and Business Administration, Ghent Univ., Tweekerkenstraat 2, 9000 Ghent, Belgium.
2. Professor, Dept. of Management Information Science and Operations Management, Faculty of Economics and Business Administration, Ghent Univ., Tweekerkenstraat 2, 9000 Ghent, Belgium; Technology and Operations Management Area, Vlerick Business School, Reep 1, 9000 Ghent, Belgium; and Dept. of Management Science and Innovation, Univ. College London, Gower St., London WC1E 6BT, U.K. (corresponding author).