Table 1. Mean Absolute Percentage Errors (MAPE) for USDA and Private Market Forecasts of Corn and Soybean Production, 1970-2004
               
Corn Soybeans
USDA Private USDA Private
  Forecast Forecast Difference Forecast Forecast Difference
---%--- ---%---
August
  1970-2004 5.2 5.4 -0.2 5.2 4.8 0.4
  1970-1984 5.9 7.0 -1.1 4.9 4.8 0.1
  1985-2004 4.6 4.1 0.5 5.4 4.8 0.6
September
  1970-2004 4.0 4.3 -0.3 4.1 4.0 0.1
  1970-1984 3.9 4.2 -0.3 3.2 3.3 -0.1
  1985-2004 4.2 4.5 -0.3 4.8 4.5 0.3
October
  1970-2004 2.4 3.0 -0.6 2.3 2.8 -0.4
  1970-1984 2.4 3.1 -0.7 2.7 2.7 0.0
  1985-2004 2.3 2.9 -0.6 2.1 2.8 -0.7
November
  1970-2004 1.2 1.5 -0.4 1.4 1.5 -0.1
  1970-1984 1.3 1.8 -0.4 1.8 2.1 -0.2
  1985-2004 1.0 1.4 -0.4   1.1 1.1 0.0
Note: Difference is calculated as USDA minus private market.  Hence, a negative difference shows that the mean abolute error of the USDA was smaller than the mean absolute error of the private market and vice versa.