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Abstract

This report mm•ins lbe reaults of five metbodok,gicel lbldies carried oat ia different COllllbies in Africa during lbe c:oune of 1987. The participating CIDlllllries were: Benin, Centrel Africu Republic, Keay,. N°Jger and z.imbabwe. Each COlllllry carried out lbe study, using a common experimenteJ design, with the objective of comparing crop esti -mates bued on the classic 'crop-cut' method with estimates -obtained by asking fanners direc:tly to state their production. Both types of estimates were compared egainst a com -plete barvest and weighing of the sampled plots. The objective of the study was to test the hypothesis that estimates of production ob­tained by interviewing farmers could be at least es accurate as estimates obtained through physical measurement involving crop-cutting on sample subplots. If this could be demonstrated, it would make pos­ul>le the introduction of a number of cheaper ud more efficient improvements to the sample design ud to the manner in which large-scale production surveys arc executed. The data from all five studies were pooled ud analyzed together. They gave the following results: 1) Estimates based on square -cuts ap -pear to result in serious over-esti -mates - by around 30%. There is considerable variability among countries however with the over-estimate ranging from 15-40%. 2) Farmers estimates are n:marbbly dOIC to ac:tua1 production figures in all countries, varying from -8% to + 7%. They also display considerably smaller variances than the crop-cut estimates. 3) Farmers estimates obtained before harvest. (forecasts) arc also good at pmlic::ting production levels but are subject to significantly greater variance. 4) Farmers estimates of planted area do not appear to provide a viable alternative to objective area measurements and gave very considerable over-estimates. When analyzed separately, each of the five country studies confirmed ud supported the overall conclusions noted above. The results, thus, strongly support the study hypothesis and indicate that, under a wide range of ge -ograpbical, soc:ial, ud administrative condi -lions, farmers' post harvest estimates per­formed in a superior fCl$hion to the so -called objective method both in terms of predicting the average value ud hawig a smaller variance.

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