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S Illinois | They do use empirical data just not at the field level. They are comparing their data to previous years using the yield at the state and national level. So your data point is combined with all of the other IA field data. NASS “knows” that their IA field observations are historically X many bushels off and adjust for it. The key to their data is collection consistency. Now they could go back and try at the field level to get the farmer found field average, but it would add trusting completely what the farmer says the yield was for that field. This is exactly what NASS doesn’t want with their field survey, which is to add any type of subjective farmer input. All they want is that non-subjective small plot data of which they can control the sampling parameters completely. Those field observations are only part of what is used to come up with the state and national yields.
A good read and listen for more info: https://will.illinois.edu/agriculture/note/how-usda-nass-gathers-cro...
As to your yield monitor not showing anything like they found, they are looking at single row strips of
30-35 ears. Very easy for a sample that is taken that way to over estimate. | |
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USDA fall estimate vs. actual yield (field in the "survey")
