Are Revisions to USDA Crop Production Forecasts Smoothed?
用Nordhaus框架检验美国农业部玉米和大豆产量预测修正的效率，发现修正存在正自相关和方向一致性，即被“平滑”，且平滑导致的预测精度损失在统计和经济上显著。
This article uses Nordhaus' framework to determine the efficiency of the revision process for USDA corn and soybean production forecasts over the 1970/1971 through 2004/2005 marketing years. Positive autocorrelation and consistency of directional changes in forecast revisions suggest these forecasts are “smoothed.” Evidence is provided that the loss in forecast accuracy due to smoothing is statistically and economically significant in several cases. A conservative bias in farm operators' assessments of yield potential and in the procedure for translating enumerator's information about plant fruit counts into objective yield estimates are identified as plausible sources of smoothing.