More on state by state numbers, now for Soybeans

The 5 state numbers for soybeans show a similar pattern to corn below. Again Iowa sows the biggest changes so far. Again, I'm not ready to attribute this to greater fluctuations in soybean conditions just yet, it could also be the sensitivity of the parameters. Many analysts who use this data simply create a fixed weight index where Index=1*very poor + 2* poor + 3*fair + 4*good + 5*excellent and do this at a national level. I do each state individually and estimate the weights individually with the only constraint in estimation that they have to be non-decreasing with condition.

I also include a variable on trend and may include a variable on planting progress. It is the parameter on planting progress which got me into so much trouble last year as Illinois had the biggest planting delay in 4 decades but had reasonably cool and moist temperatures the rest of the year which lead to better yields than my simple model would have anticipated. The planting progress is basically an intercept shift. If you want to read more on Illinois crop yields from last year I'd suggest the folks at U of Illinois who do far more detailed models than I do here.

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?

Week 18

Corn and soybeans estimates are converging as we would expect as we approach the end of September where the equations were estimated. So the corrected model shows a modest increase for corn yields while the uncorrected model shows a modest decline. Why? Because although conditions in aggregate may have slipped slightly this week, the decline was less than the historical average during this week and thus the corrected model, which is the best guess, shows a bit of improvement.

Just to clarify, if conditions NEVER changed through the year, the uncorrected line would be a flat line while the corrected model would rise to meet it.

The hot weather in cotton country shows up with a decline in both cotton yields and production. I always hesitate to take one week as a indicator of actual change, so this one will bear watching. If unfavorable temperatures continue, we should see a steady decline here. I'll be posting again on Monday of next week and then again after the USDA report on the 12th to see how close I am to USDA

Week18 Spreadsheet (xls 3mb)

Week17

Corn yield includes the trade estimates for the last few weeks as green dots. I'm in the middle of the trades range. One way to look at is I'm going to be closer than at least half of them.

Last week somebody picked up this blog and reported that last week despite US conditions falling, my results showed and increase in yields. I found this curious so lets take a look.

At the national level, these were the results (comparing July 18 to July 11). So very modest declines, but declines none the less.

-----------------------------------------------------------------------------
State      : Very poor :   Poor    :   Fair    :   Good    : Excellent
-----------------------------------------------------------------------------

18 States .......:     2           7          19          51          21                                                        
Previous week ...:     2           7          18          52          21

The model is a state level model, however, so lets look at the key state breakouts.
First July 11th.

-----------------------------------------------------------------------------
State      : Very poor :   Poor    :   Fair    :   Good    : Excellent
-----------------------------------------------------------------------------
Illinois ........:     3           9          23          47          18
Indiana .........:     3           9          26          46          16
Iowa ............:     3           7          19          51          20
Minnesota .......:     -           3           9          57          31
Missouri ........:     6          16          28          36          14
Nebraska ........:     1           3          10          64          22
Ohio ............:     2           9          25          47          17

Now July 18th.

-----------------------------------------------------------------------------
State      : Very poor :   Poor    :   Fair    :   Good    : Excellent
-----------------------------------------------------------------------------
Illinois ........:     2           8          23          49          18
Indiana .........:     4           9          25          45          17
Iowa ............:     3           8          20          48          21
Minnesota .......:     -           2           8          55          35
Missouri ........:     5          16          31          40           8
Nebraska ........:     1           3          12          63          21
Ohio ............:     2           9          25          48          16

When comparing them by state it is a bit of a mixed bag. The US total condition numbers are weighted by acreage but an extra acre in excellent condition in Iowa probably more than makes up for an acre falling to good condition in most other states. But even in Iowa it is a mixed bag. The difference between fair and good is not the same number of bushels improvement as between good and excellent.

This is true for all states so while the average acre may have seen a very slight decline in the US condition numbers, the state specific changes matter. If this was a single equation national level model, then I might have expected yields to change, but I do each state individually so exactly where conditions change matters.

Week 17 Spreadsheet (3mb)

Week 16

All crop yield and production numbers showed positive change this week.
I'll add some additional state by state analysis in upcoming posts.

Week 16 Spreadsheet (3mb)

Week 15

Just as a reminder, the large spreadsheet with the state by state numbers for the corrected and uncorrected model is available at the link below. I included the yield and production numbers from the latest WASDE report on the graph. No updates on yields for corn and soybeans, but the production numbers do reflect the updated area for these two crops. I discussed the updated cotton numbers in my previous post. The corrected model was spot on relative to the USDA and much closer than the trade estimates (green dots), which at this early stage probably means little other than the crop in the field has really great potential.

There was overall improvement in all three crops this week. Nothing dramatic in the aggregates, some changes on a state by state basis.

Week 15 Spreadsheet (3mb)

Spot on for cotton

I was very close to USDA's cotton production estimate released this week. USDA gives a crop of 18.3 million bales and the corrected model, which is really the 'best guess' was right there at 18.31. This is a good way to clarify again the two different models. The corrected model is the best guess for the crop, understanding that there is often some decline in conditions throughout the year and this is incorporated, just as a USDA estimate should naturally include this when they estimate their relationships in predicting final yield. Alternatively, the uncorrected model is the crop in the field in today's conditions, no forward look as to where it is likely to head. This is in some ways the potential of the crop. If conditions stayed the same (which historically is unlikely) this is what the yield would be. So when folks are talking about the potential of this crop this may be closer to that upside.

This is a big number and adjustment from the USDA which may also signal some of that potential in the cotton crop. I've historically had trouble with the cotton numbers. Last year the model seemed to do quite well but there are some features of cotton when compared to corn and soybeans that make estimates more difficult. I think the one thing you can take away from what the model suggests as well as industry talk is that the current crop has the potential to be quite large. Is 19 million bales possible?

(Green dots are yesterday's trade estimates which ranged from 17.0 to 17.9 million bales)