1. A.T. Kearney GmbH, D-40211 Düsseldorf, Germany; and Chair of Logistics Management, Gutenberg School of Management and Economics, Johannes Gutenberg University Mainz, D-55128 Mainz, Germany
2. Chair of Logistics Management, Gutenberg School of Management and Economics, Johannes Gutenberg University Mainz, D-55128 Mainz, Germany