Corn trend yields from the model

Calculating simple trend yields is fraught with danger. The selection of the starting or ending year can have significant influence. There are still issues with using conditions to 'correct' for this but in the model I do estimate an underlying annual trend based on the 1986-2008 period. What follows are the estimated annual trend yield improvements for corn out of the model. I'll follow up with soybeans and cotton as I take the opportunity to use this blog to explain the model.
All results are expressed as bushes of corn/acre/year
AL 1.65 bu/ac/year
CO ~0
GA 2.06
IL 2.67
IA 2.74
IN 2.16
KS 1.43
KY 1.93
MI 1.96
MN 2.48
MS 2.75
MO 2.22
NE 1.95
NC 1.16
PA 0.97
OH 2.18
SC ~0
SD 2.84
TN 2.02
TX 1.95
WI 1.83