“…However, in some cases, some (good) outputs should be maximized or some (bad) outputs should be minimized simultaneously. Literature in DEA refers to bad outputs as undesirable factors (Seiford and Zhu, 2002). One can find a number of undesirable output examples in the empirical literature such as delayed flight (Coli et al, 2011), poverty rate (Bruni et al, 2011), patient deaths (Yawe and Kavuma, 2008), power interruptions and emissions such as SOx (Burnett and Hansen, 2008;Korhonen and Luptacik, 2004;Zhou et al, 2007), SO2, NOx and CO2 (Kortelainen and Kuosmanen, 2007;Sueyoshi and Goto, 2013;Tyteca, 1997), NOx (Oggioni et al, 2011;Tyteca, 1996) COx gases (Oude Lansink and Bezlepkin, 2003;Zaim and Taskin, 2000).…”