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Research on transportation investments has focused on estimating their average effects, mostly in middle and high income countries. But the return to infrastructure investment depends on context: in the case of building roads, returns clearly vary as a function of the places that they connect.
Using new data on roads and cities spanning over 50 years in 39 African countries, Remi Jedwab and colleagues document the effect of road construction on city population growth, through the channel of increasing market access. They estimate a 30-year elasticity of city population with respect to market access that is smaller than found in other regions. But they also find heterogeneity in returns within Africa that provides important insights about the potential return to specific transport investments, depending on context.