“…Their model was first extended by Fields (1975), which allowed for on-the-job search from rural agriculture, the existence of an urban informal sector, preferential hiring of the better-educated, and employment fixity. The model has subsequently been extended and generalized to allow for duality within the rural sector, mobile capital, endogenous urban wage setting, riskaversion, a system of demand for goods, and many other factors (Corden and Findlay, 1975;Calvo, 1978;Moene, 1988Moene, , 1992Khan, 1989;Fields, 1989;Chakravarty and Dutta, 1990;Bourguignon, 1990;Basu, 1997).…”