with Scott Irwin, Agricultural Economist - University of Illinois
There is a long-standing market saying that "big crops get bigger and small crops get smaller." This statement refers to the yield forecasting cycle of the USDA's National Agricultural Statistics Service (NASS). That cycle for corn and soybeans consists of monthly yield forecasts that begin in August and extend through November and culminate with the final yield estimate for the season that is released in January following harvest. Specifically, the statement implies that early NASS yield forecasts are "conservative" in years when yields are high and get larger as the forecast cycle progresses and are "optimistic" in years when yields are low and get smaller as the forecast cycle progresses. These notions are tied to the more general idea that NASS yield forecasts are "smoothed," meaning that the final yield estimate results from cumulative monthly changes in forecasts in the same direction. Some tend to believe that smoothing of NASS yield forecasts, particularly in years of yield extremes, is intentional in order to minimize or spread the price impact of very large or small yields. Alternatively, yield forecasts may appear to be intentionally smoothed simply due to the fact that forecasts become more accurate during the forecast cycle as more actual yield information is incorporated into the forecasts.