1. New York University Leonard N. Stern School of Business , Tisch Hall, 40 West Fourth Street, 714, New York, NY 10012, USA . e-mail: gc59@stern.nyu.edu
2. University of Pavia and ICRIOS-Bocconi University , Via San Felice 5, Pavia 27100, Italy. e-mail: roberto.fontana@unipv.it
3. Bocconi University , Via Roentgen 1, Milano 20136, Italy. e-mail: franco.malerba@unibocconi.it