“…Different versions of these models have been used in the last few years (Blundell and Meghir, 1987;Jones, 1989;Blaylock and Blisard, 1992;Gould, 1992;Blisard and Blaylock, 1993;Lin and Milon, 1993;Burton et al, 1994;Yen, 1994;Gao et al, 1995;Yen, 1995;Yen and Su, 1995;Burton et al, 1996;Ramajo, 1996;Su and Yen, 1996;Wang et al, 1996;Yen and Jones, 1997).…”