Death comes to us all. Life's but a walking shadow | It seems to me that due to Iowa's persistent dryness, Iowa's corn yield is one major unanswered question toward this year's yield and production. If you do multiple regression analysis of week 31 condition scores on Iowa corn yields you see that trend alone accounts for about 64% of the variation in yield between 1986 & 2016 while trend together with week 31 condition scores accounts for about 90% of the variation in yield. This suggest that condition scores capture about 29% of the observed variation in yields, second table below. A graph of observed yield vs the "predicted" yield indicates that in general, week 31 condition scores reasonably well accounts for the direction if not the magnitude of the deviation from the expected trend line yield. It appears that generally, conditions scores underestimates both the positive and negative deviations from trend. particularly in years where yields were extreme. You can imagine that the persons making the observations very well might underestimate yields in good years and overestimate yields in poor years.
Week 31 condition scores for Iowa give an estimated yield of 185 bpa with a standard deviation of 8 bpa. If you assume that growing conditions in Iowa are less than favorable then you might conclude that based on conditions yields in Iowa may be as much as 8-10 less than condition scores suggest, namely 175 to 185 bpa, well within the range of yield observed in the past ten years.
Note: edited to correct my original post, the data is week 31 conditions scores not week 32.
Edited by 1234 8/8/2017 06:16
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 (iowa yld vs cond score graph-page-001.jpg)
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 iowa wk 32 condition scores vs yld-page-001.jpg (105KB - 37 downloads)
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iowa yld vs cond score graph-page-001.jpg (74KB - 44 downloads)
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With reference to condition scores below, Iowa corn yield
