The earliest contribution to the theory of economic development and its structural transformation is attributed to William Petty (1623-1689)and Friederich List (1789-1846). However, modern analysis of sectoral transformation originated with A.G.B. Fisher (1935, 1939) and Colin Clark (1940) who dealt with the sectoral shifts in terms of their composition of labour force. Using the tri-chotomised sectoral classification of an economy into primary, secondary and tertiary sectors, Fisher and Clark explain the reallocation of workforce during the period of modern economic growth. According to them, as economies developed there will be shift in the share of workforce initially from primary (agriculture) to secondary sector and later to the tertiary sector.