Table 1. Mean Absolute Percentage Errors (MAPE) for USDA and Private Market Forecasts of Corn and Soybean Production, 1970-2005
               
Corn Soybeans
USDA Private USDA Private
  Forecast Forecast Difference Forecast Forecast Difference
---%--- ---%---
August
  1970-2005 5.2 5.4 -0.2 5.3 4.9 0.4
  1970-1984 5.9 7.0 -1.1 4.9 4.8 0.1
  1985-2005 4.8 4.3 0.5 5.6 5.0 0.6
  2001-2005 3.7 4.0 -0.3 8.2 7.9 0.3
September
  1970-2005 4.1 4.4 -0.4 4.2 4.1 0.1
  1970-1984 3.9 4.2 -0.3 3.2 3.3 -0.1
  1985-2005 4.2 4.6 -0.4 4.9 4.7 0.2
  2001-2005 3.5 4.4 -0.9 6.2 6.8 -0.6
October
  1970-2005 2.4 3.0 -0.6 2.4 2.8 -0.4
  1970-1984 2.4 3.1 -0.7 2.7 2.7 0.0
  1985-2005 2.3 2.9 -0.5 2.2 2.8 -0.6
  2001-2005 1.2 2.1 -0.8 2.1 3.1 -1.0
November
  1970-2005 1.1 1.5 -0.4 1.4 1.5 -0.1
  1970-1984 1.3 1.8 -0.4 1.8 2.1 -0.2
  1985-2005 1.0 1.4 -0.4 1.1 1.1 0.0
  2001-2005 0.7 0.8 -0.2   1.1 0.9 0.2
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.