This study quantifies how population density affects input use and output per hectare of staple crops. In doing so, we empirically test Ester Boserup’s (1965) hypothesis that increasing population density leads to agricultural intensification, measured through increased demand for modern inputs, such as commercial fertilizer and increased production per hectare. We test these effects using geospatial data on population density1. We also use recently collected household-level panel data from Malawi and Zambia to explore how population density affects household outcomes of interest. We conduct separate estimates for Malawi and Zambia and then compare and contrast our findings for the two countries. As Malawi is a country of high population density and Zambia is a country of low population density, having results from both countries provides a robust understanding of how population growth affects smallholder intensification in different settings within the region.