1. USDA Crop Progress out today. Time to compare to the forecast I made this morning. To recap, USDA reported corn planting progress at 51% as of Sunday. My simple method forecast was 43%. Where did I go wrong? 
2. My simple method involves forecasting the two components of weekly corn planting progress: i) # of suitable field days, and ii) % progress per suitable field day. Basic idea is to focus on # suitable field days and assume rate per day is the historical average. I
3. I assumed 3 suitable field days and the historical average of 5.3% for rate of progress per day. This gave a gain in corn planting progress of 16% versus the actual of 24%. Note that US corn planting progress this year has been well above average last couple of weeks.
4. Let's start with rate of corn planting progress per suitable field day. Man, 2020 has been spot on the historical average rate of corn planting progress per suitable field day. Last week (#18) was 5% per suitable field day, a smidgen less than historic average of 5.3%.
5. Here is the chart for # of suitable field days in a week. Now we are getting somewhere. Acre-weighted suitable field days for US has been way, way above historic average for almost entire planting season to date in 2020. Last week 4.9 suitable field days vs. average of 3.9
6. So, the answer to why my planting progress forecast for last week was off was that I severely underestimated the number of suitable field days across the US. I said 3 when it was 4.9. Big miss. Going to have to do some more work there!
7. Despite my error this week I think the simple method that TH and I developed has merit as a tool to forecasting corn planting progress. The key is to monitor weather during the week and get a better handle on suitable field days state by state. Will try again next week!
8. Link to #FDD article with full details on our method of forecasting US corn planting progress farmdocdaily.illinois.edu/2020/04/a-simp…
