USDA'slatest crop progress and condition report rated the U.S. corn crop 56% in the good or excellent category, up 1% from the prior week.
Crop ratings have held remarkably consistent for most of this year albeit at the lowest levels since 2012.
Crop conditions are measured using our usual ratings system where we weight the crop based on the percent in each category and assign that category a factor of 2 for very poor, 4 for poor, 6 for fair, 8 for good, and 10 for excellent and then sum the results.
This graphic is a scatterplot of week 41, or middle of October, U.S. corn crop conditions vs the percent that yields deviated from the 35-year trend.
There is a decent correlation of 79.3% but the linear R squared is a less than desirable 62.9% though a polynomial R squared is a better 66.1% which is what is depicted here.
Also by the middle of October, due to the advanced state of the corn crop, USDA has in the past not published week 41 crop conditions and in recent years this has been the case for 2013, 2012, 2010 and prior to that all years between 1997 and 2002.
For the years that are presented in this study, there are four seasons where as now week 41 or middle of October U.S. corn crop ratings have been below the 700 level.
This includes the lowest rated year of 1993 which, like 2019, was a growing season characterized by very heavy precipitation with a rating of 662 and final yields were 17.3% below trend; 2003 when a rating of 672 resulted in final yields that season 1.1% above trend; 2005 where a rating of 698 still had final yields that year 2.3% above trend; and 2011 with a rating of 678 and yields off 5.8% from trend.
This year USDA has pegged the the 2019 U.S. corn yield at 168.4 bushels per acre (bpa) which we calculate as being 1.8% below trend, yet a perfect fit on the trendline would calculate to a 168.0 bpa yield.
This regression study along with more updated yield reports that often indicate corn yields below recent seasons but certainly better than expected suggests the USDA yield estimate given earlier this month may not change that much in November and January crop reports.