Monday, October 5, 2009

Week 27 results

Note the post after this one where I correct a question I had about how the 18 state totals are calculated. I know I've had that discussion in the past but I still made a incorrect statement about weighting. It is done on last years planted acres. Now my parameters are not fixed relative to each other that is to say Yield = a + b1(Poor) + b2(Fair) + b3(Good) + b4(Excellent) + b5(planting progress term) + b6(trend), etc. The parameters b1 through b4 are not restricted other than they must increase in value by some very nominal (essentially zero) amount. Please recall that I do this on a PLANTED AREA YIELD with a separate abandonment equation, not so important for corn and soybeans but more important for cotton. They are in bushels and the parameter values are basically the yield difference between the category in question and that in (Very Poor). So if b4=110, the difference in yield between an acre in Very Poor condition and that in Excellent is 110. But is is possible that b2 is only marginally greater than b3 or b4 only marginally greater than b3, etc. So not all condition movements have the same effect on yields and are not constrained across states, so when the 18 state total didn't move much last week, some states moved up while others moved down, this is enough for me to see a greater change that I might in an 18 state total model.

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