[1] Vienna Univ Technol, Inst Stat & Math Methods Econ, Dept Operat Res & Control Syst, A-1040 Vienna, Austria
[2] Univ Vienna, Dept Business Adm, Vienna, Austria
[3] ESSEC Business Sch, Cergy Pontoise, France
[4] Austrian Acad Sci, Vienna Inst Demog, Wittgenstein Ctr Demog & Global Human Capital, IIASA,VID OAW WU, A-1010 Vienna, Austria