[1] Univ Barcelona, AQR IREA Inst Appl Econ Res, Diagonal 690, Barcelona 08034, Spain
[2] Univ Politecn Cataluna, Dept Signal Theory & Commun, Jordi Girona 1-3, Barcelona 08034, Spain
[3] Univ Barcelona, Dept Econometr & Stat, Riskctr IREA, Diagonal 690, Barcelona 08034, Spain
[4] Univ Barcelona, Dept Econometr, Diagonal 690, Barcelona 08034, Spain