Data Source
- NASS corn grain yield (1980-2016) at county and agricultural district (AD) level in Illinios (Bu/acre)
- NASS corn harvested area (1980-2016) at county and agricultural district level in Illinios (acre)
- Productivity = yield \(\times\) harvested area
- Nine ADs in IL
- Sum county level productivity to AD level and compare with productivity calculated at AD level