Yield reducing factors that may contribute to errors in model simulations could be associated with disease and pest infestation that are unaccounted for in remote sensing or the crop model. Another factor that has an effect on yield is the presence of weeds, which cannot be assessed from lower resolution satellite imagery. A major consideration to be noted is that NASS yield statistics are designed to provide very accurate estimates at the State level. County level yields are estimated and adjusted to sum to the State level.