The Lewis Model: A 60-Year Retrospective

The Lewis model has remained, for more than half a century, one of the dominant theories of development economics. This paper argues that the power of the model lies in the simplicity of its central insight: that poor countries contain enclaves of economic activity just as rich countries contain enclaves of poverty; and that a proximate explanation for the difference in income per capita across countries is that there are large differences in the relative sizes of their "modern" and "traditional" sectors. But while the Lewis model contains a powerful and compelling macro narrative, its details have proved somewhat elusive to scholars and students who have followed, and its policy implications are unclear. This paper identifies several key insights of the Lewis model, discusses several different interpretations of the model, and then reviews modern evidence for the central propositions of the model. In closing, we consider the relevance of Lewis for current thinking about development strategies and policies.