In the end the 2002 USDA report struggled to explain why there had been such a rapid uptake of GM crops in the US, although it refers to a possible 'convenience' factor. However, a separate study funded by Iowa State University carried out in 1998 reveals that GM crop uptake can be driven as much by how well farmers believe the crops deliver, as by factual data on their real performance. In the world of commerce and marketing perception is, of course, everything.
The Iowa study confirmed that over half of farmers planting herbicide-tolerant GM soya did so because they believed that it gave them higher yields compared to conventional varieties. However, when the university analysed the harvest results of the farms concerned they found the opposite was true despite the belief of the farmers to the contrary (it is in fact now recognised that the 'glyphosate resistance' genetic modification introduced in the 1990s had actually reduced the yield potential of GM soya by inadvertently disturbing other aspects of the plant's functioning).
A subsequent study from the University looked in detail at the on-farm financial performance of soya crops in Iowa. It confirmed that after taking into account costs relating to seed, herbicides, fertiliser, all machinery operations, insurance, and a land charge "there is essentially no difference in costs between the tolerant and non-tolerant fields". However, because of their higher yields the non-GM crops made a profit for their growers, whereas the GM varieties did not.