ABSTRACT
The title of this essay succinctly states its purpose: to show that the work done by Joan Robinson on labour mobility in the thirties is an important precursor of the internal migration modelling started in the late 1960s to explain the rising urban unemployment in the developing countries. It is pointed out that the Hicksian wage differential approach had been challenged by the chance-to-be-employed approach long before Harris and Todaro attempted to substitute their employment probability model for the Lewisian wage gap model.
