Beyond the “inverse relationship”: Area mismeasurement may affect actual productivity, not just how we understand it

Measurement error in agricultural field area and productivity data for developing countries is widely acknowledged, but there is a shortage of evidence on what this implies, especially for farmers. By comparing self‐reported to global positioning system measurements, we investigate area measurement errors using a nationally representative dataset of Zambian smallholder maize plots. We examine the implications for researchers’ understanding of productivity, but also how actual productivity may be affected. We find land area tends to be overstated on smaller fields and understated on larger fields. Correcting measurement error strengthens evidence of an inverse relationship between field size and productivity. Input use patterns indicate farmers believe the inaccurately reported area figures, suggesting measurement errors affect input choices and thus actual productivity. Improving farmer understanding of area measurements could improve productivity. Improving the accuracy of area data will improve researchers’ understanding of productivity.