Table 2. Root Mean Squared Percentage Errors (RMSPE) 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 7.4 8.0 -0.6 6.5 6.7 -0.2
  1970-1984 8.7 9.9 -1.2 6.2 6.3 -0.1
  1985-2005 6.3 6.2 0.1 6.8 7.0 -0.2
  2001-2005 4.7 5.2 -0.5 10.1 11.3 -1.2
September
  1970-2005 5.1 5.6 -0.6 4.9 5.2 -0.3
  1970-1984 4.5 5.0 -0.5 4.0 4.5 -0.6
  1985-2005 5.5 6.1 -0.6 5.5 5.7 -0.2
  2001-2005 4.1 4.9 -0.8 7.0 8.2 -1.2
October
  1970-2005 3.2 3.8 -0.6 2.8 3.3 -0.5
  1970-1984 2.8 3.4 -0.7 3.1 3.3 -0.2
  1985-2005 3.5 4.0 -0.5 2.6 3.4 -0.8
  2001-2005 1.4 2.4 -1.0 2.4 3.7 -1.3
November
  1970-2005 1.6 2.1 -0.5 1.8 2.0 -0.2
  1970-1984 1.6 2.0 -0.4 2.3 2.7 -0.3
  1985-2005 1.5 2.2 -0.6 1.3 1.4 -0.1
  2001-2005 0.9 1.1 -0.3   1.2 1.2 0.0
Note: Difference is calculated as USDA minus private market.  Hence, a negative difference shows that the root mean squared error of the USDA was smaller than the root mean squared error of the private market and vice versa.