1. Departament of Economics, University of Zaragoza, Zaragoza, Spain
2. Institute for Biocomputation and Physics of Complex Networks (BIFI), Zaragoza, Spain
3. Institute of Labor Economics (IZA), Bonn, Germany
4. ARAID Foundation, Diputación General De Aragón, Zaragoza, Spain
5. Departament of Theoretical Physics, University of Zaragoza, Zaragoza, Spain