Thursday, October 15, 2009

So where did it 'all go wrong' ?

So I'm pretty far away from the USDA estimates and this last October report moved them even further away from me. The model has performed quite well in previous years and so this of course make me curious as to what was going on and where the differences were. I should point out here that I DO NOT adjust the model during the season, but I do re-estimate the parameters each year.

Well it is clear that one big source of difference is the Illinois corn yield. I currently have 163.1 bu/ac in my corrected model while the USDA is running 179 bu/ac. Is it conditions? Well conditions don't tell much of the story. In 2004 IL yield was 180, in 2008 it was 179 so while trend yields are important here (I'm running 2.7 bu/ac growth annually) lets set that aside for the moment and look at conditions for this week in history.

2004: VP-1 P-2 F-13 G-57 E-27
2008: VP-1 P-4 F-23 G-52 E-20
2009: VP-1 P-6 F-28 G-52 E-13

So conditions are worse than those previous years. So while conditions could still be it, lets look at what I'm getting from the other variable, planting progress. Because this is just a hobby, I search for the most significant planting progress percent among a number of weeks for each state. I try to make the date later as I go north in the states. Well I used the week May 6-12 percent planted for Illinois this year. Now the high in this week over the last five years is 95%, the low is last year at 60%...This year? 10%. This is giving me one heck of a yield hit. If I simply go in and put the 5 year average for planting progress in for Illinois (78.8% planted) my new Illinois yield is 177.7 bushels an acre. Within 1.5 bushels of the USDA estimate. While that doesn't solve everything, it does put me closer to USDA, here is my total if I make that simple change. Now this week, the numbers from the USDA STILL put me quite far off, but I'm a more reasonable distance from the estimate.

Using the average planting progress of the last 5 years JUST for Illinois

So, clearly the USDA estimate suggests I have far to0 much of an impact on terminal yield based on planting progress. This could be because I have the wrong 'week' as the indicator, but planting was delayed across all the weeks to some extent. Maybe it is because farmers can get into the fields and get it all planted more quickly now than before, or maybe the seed technology is different. Or it could be that in previous years, delayed planting resulted in freeze issues that are not materializing this year, or, was the weather just cooperative this year and we didn't have the 'hot and dry' spell that would have crushed a late planted crop?

The same issue is present for IN and MI, but I'm using a bit later week for OH and planting progress was about 'normal' this week and thus you will note that I'm actually above USDA. While there are still several weeks left, I'm not sure I hold much hope to close that much of a gap. What I can say is that planting progress is playing a bigger role this year than I anticipated it would.

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