Using 1971-2000 data, we examine the accuracy of corn and soybean production forecasts provided by the USD A and two private agencies. All agencies improved their forecasts as the harvest progressed, and forecast errors were highly correlated and unbiased. The relative forecast accuracy of the agencies varied by crop and month. For corn, USDA's forecasts ranked as most accurate of the three agencies in all periods except for August during the recent period and improved most markedly as harvest progressed. For soybeans, forecast errors were very similar, with the private agencies ranking as most accurate for August and September and making largest relative improvements for August during the recent period. The USDA forecasts were dominant for October and November. Our findings identify several patterns of relative forecast accuracy that have implications for private and public decision makers.
