Short note on state by state numbers.

The Iowa yield numbers are significantly higher than those for Illinois but have also show significant variation so far. I don't attribute that to big changes in Iowa as much as I might attribute it to problems with equation parameters. Maybe there is a to big a yield difference between some of the condition categories?

If we lay out the Iowa equation, the Very poor category is the base.
when we go to poor we add +0, so no change in yields, I can't determine any real difference between very poor and poor. The same is true with fair at +0, but good adds +30bu per acre and excellent adds +66 bushels per acre. It could also be there there are just isn't a lot of Iowa that is in very poor or poor condition.

For Illinois we have (again with very poor as the base) poor +0, fair +26, good + 69.1, excellent 69.8 so a much different gradient depending on condition shifts.

Also to add to the discussion , here are the trend yields in corn and soybeans for the top 5 production corn states (in 2007) and also my home state of Missouri. These are the underlying annual trend growth I estimate in the equations. This should be adjusted for conditions and thus starting and ending year are less relevant, but probably not inconsequential.


State-corn trend yield-soybean trend yield

IL - 2.94 bu/ac - 0.47 bu/ac
IA - 2.66 bu/ac - 0.53 bu/ac
IN - 2.32 bu/ac - 0.63 bu/ac
NE - 2.05 bu/ac - 0.74 bu/ac
MN - 2.47 bu/ac - 0.24 bu/ac
MO - 2.21 bu/ac - 0.51 bu/ac

The numbers I show for Iowa would be a little lower than estimated last year and the ones for Illinois might be a bit higher, you can see what I used last year in the archives.

You can click on the table below to enlarge it. It is a state by state reporting of the corrected model production and yield for corn as of this week. I'll update it in next week. Feel free to print it out and pencil in your own guess, how about some anonymous postings on what YOU think the USDA yield will be?