It is essential to develope accurate input-output data when using mathematical decision models that utilize enterprise budgets. One of the most important items of input-output budgets for crop enterprises is yield. A realistic yield is also one of the most difficult items to derive. An analysis of cotton yields from 30 individual farms for the 10 year period, 1971-80, indicates that it is not possible to derive yield data that is representative of farms in general. Yield data from the individual farm is to be preferred for farm level planning.