Talip Kilic, The World Bank
"Could the Debate Be Over? Errors in Farmer-Reported Production and Their Implications for Inverse Scale - Productivity Relationship in Uganda"
Based on a two-round household panel survey conducted in Eastern Uganda to test the relative accuracy of subjective approaches to data collection vis-à-vis objective survey methods for maize yield measurement, soil fertility assessment and maize variety identification, this study shows that the analysis of the inverse scale-productivity relationship is highly sensitive to how maize production and thereby maize yield (anchored in GPS-based plot area measurement) are measured. While farmer-reported production-based plot-level maize yield regressions consistently lend support to the inverse scale-productivity relationship, the comparable regressions estimated with maize yields based on sub-plot crop cutting, full-plot crop cutting, and high-resolution satellite imagery-based remote sensing point towards constant returns to scale.
In deriving the much-debated coefficient for GPS-based plot area, the regressions control for objective measures of soil fertility, maize genetic heterogeneity and edge effects at the plot-level; a rich set of plot, household and plot manager attributes; and time-invariant household- and parcel-level unobserved heterogeneity in select specifications that exploit the panel nature of the data. The core finding is driven by persistent over-estimation of farmer-reported maize production and yield vis-à-vis their crop cutting-based counterparts, particularly in the lower half of the plot area distribution. Though the findings contribute to a larger, and renewed, body of literature questioning the inverse scale-productivity relationship based on omitted explanatory variables or alternative formulations of the agricultural productivity measure, our paper is among the first documenting how the inverse relationship could be driven by errors in self-reported survey data on crop production.
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