Lucas, Robert E.B.2020-05-182020-05-1819840281—6814https://hdl.handle.net/2144/40980African Studies Center Working Paper No. 70INTRODUCTION The hypothesis presented in Todaro (1969), that the likelihood of finding work in town influences the rate of rural-urban migration, now enjoys the status of a received doctrine. Assuming potential migrants indeed respond to this employment probability, the model of Harris and Todaro (1970) demonstrates that, in certain parametric ranges, urban job creation may actually exacerbate unemployment and even reduce national product. This result has had considerable influence on policy formulation in LDC, by emphasizing that, in the urban sector, the social opportunity cost of labor may not be insignificant despite burgeoning unemployment. Yet neither the Todaro hypothesis nor prevalence of the Harris-Todaro parametric range has been adequately, empirically explored. Many estimates of macro migration equations do exist, normally relating the proportion of population migrating to average wages in differing locations and occasionally to average population characteristics. But in Lucas (1975), I show that the popular nonlinear specification of such macro functions may well display serious specification error bias; a nonlinear function of the aggregate variables is not simply the average of underlying micro migration decisions related to the disaggregated variables. Thus, although a few estimates of macro migration equations have also incorporated average unemployment rates, usually in developed country contexts and with mixed results, these analyses are at best very circumscribed tests of the Todaro and Harris-Todaro theories. [TRUNCATED]en-USCopyright © 1983, by the author.BotswanaMigrationMigrant laborBatswanaSouth AfricaArticle