How Big of an anomaly is the Illinois Corn Yield at 225?

A customer recently asked me what Illinois' highest yield was before the USDA projected Illinois' yield at 225 bushels per acre in the August WASDE data release. That question got me thinking about Illinois’ trendline, and I wanted to share what I found.

So first of all, in terms of Illinois’ highest projected yield, the state was projected to have a yield of 215 bushels per acre in November 2022, before the final yield in January was lowered to 214. There have been two other times Illinois' yield was estimated at 214 mid-season before being lowered in the final estimates -- 206 in 2023 and 210 in 2018.

In summary, this estimate of 225 bushels an acre is 5.1% higher than the highest final yield of 214.

Summary of Yield Projections

Now, when we assemble the historical data into trendlines, the 5-year trendline for Illinois projects a 220.7 bu acre yield. However, moving back in time, this quickly falls to 211-207 bu/acre until we get back to the 12-14 year trendlines that project yields from 220-223 bu/ac. These trendlines tend to overestimate the likelihood of a 2012-style year, not fully accounting for the relative recent improvement from 2012. Based on the historical record from the last 10 to 20 years, it’s reasonable to suggest that the yield projected out to 207-208 bu/acre. In this case, the 2024 yield is projected 17 bushels per acre above trend.

Here are the specific trendlines:

The 5 year trendline projects a 2024 yield of 220.7 bu/ac

The 10 year trendline projects a 2024 yield of 207.47 bu/ac

The 15 year trendline projects a 2024 yield of 217.20 bu/ac (now including the 2012 aberration)

The 20 year trendline projects a 2024 yield of 207.66 bu/ac

The 25 year trendline projects a 2024 yield of 206.92 bu/ac

The 30 year trendline projects a 2024 yield of 206.46 bu/ac