1. School of Information, University of Texas at Austin, Austin, Texas 78701;
2. Desautels Faculty of Management, McGill University, Montreal, Quebec H3A 1G5, Canada ;
3. Management and Engineering, Huang Engineering Center, Stanford University, Stanford, California 94305-4026;
4. Department for Management, Technology and Economics, ETH Zurich, 8092 Zurich, Switzerland;
5. Technology Management, University of California, Santa Barbara, Santa Barbara, California 93106