Yields also depend on locational factors such as soil fertility, rainfall, and temperature.
Therefore, adopters and nonadopters may be systematically different and these differences may manifest themselves in farm performance and could be confounded with differences due purely to adoption. GE crops do not increase the yield potential of a hybrid. However, by protecting the plant from certain pests, GE crops can prevent yield losses compared with non-GE hybrids, particularly when infestation of susceptible pests occurs. This effect is particularly important in the case of Bt crops. The economics of chemical use were not always favorable and timely application was difficult.