2 IZA Discussion Papers
IZA Discussion Paper No. 3609
revised version published in: Proceedings of the National Academy of Science, 2009, 106 (19), 7745-7750
IZA Discussion Paper No. 2789
published in: Stefan Bender, Julia Lane, Kathryn Shaw, Fredrik Andersson, and Till Von Wachter (eds.), The Analysis of Firms and Employees: Quantitative and Qualitative Approaches, NBER and University of Chicago Press, 2008, 45-106