This paper investigates how land size measurements vary
across three common land measurement methods (farmer
estimated, Global Positioning System (GPS), and compass
and rope), and the effect of land size measurement error
on the inverse farm size relationship and input demand
functions. The analysis utilizes plot-level data from the
second wave of the Nigeria General Household Survey
Panel, as well as a supplementary land validation survey
covering a subsample of General Household Survey
Panel plots. Using this data, both GPS and self-reported
farmer estimates can be compared with the gold standard
compass and rope measurements on the same plots. The
findings indicate that GPS measurements are more reliable
than farmer estimates, where self-reported measurement
bias leads to over-reporting land sizes of small plots and
under-reporting of large plots. The error observed across
land measurement methods is nonlinear and results in
biased estimates of the inverse land size relationship.
Input demand functions that rely on self-reported land
measures significantly underestimate the effect of land on
input utilization, including fertilizer and household labor.