Personal Income and Quality Purchase Gabszewicz and Thisse(1979, 1980)and Shaked and Sutton(1982) present models based on the utility function (12. 1)with more than two possible quality levels and show that even under free sequential entry, only a small number of different-quality brands will be producedPersonal Income and Quality Purchase • Gabszewicz and Thisse (1979, 1980) and Shaked and Sutton (1982) present models based on the utility function (12.1) with more than two possible quality levels and show that even under free sequential entry, only a small number of different-quality brands will be produced