Performance Results and Characteristics of Adopters of Genetically Engineered Soybeans in Delaware

Agricultural and Resource Economics Review, Oct 2004 by Bernard, John C, Pesek, John D Jr, Fan, Chunbo

Some limitations of the study should also be noted, however. Because the survey respondents represented only a small region of the country, the results may certainly vary in the major soybeanproducing regions. Also, the slight bias in responses toward larger farms may overstate the adoption of and success with GE soybeans. Yet, despite these concerns, the results presented here provide an important contribution to the literature, especially given the significance of this crop and the limited work conducted to date examining its adoption and performance in the field.

Finally, while the results reported here are positive, it should be cautioned that a future limitation of the technology may be the emergence of glyphosate-resistant weeds. Powles et al. (1998) first discovered resistant weeds in Australia after long-term continuous use of the herbicide. Since the time of this survey in 2000, these concerns have spread to Delaware, as researchers have identified a resistant horseweed (VanGessel, 2001 ). Given the current high usage of glyphosate, this could be of paramount concern. Farmers will need to monitor this development. The problem may eventually overcome the cost savings, suggesting an avenue for future research. The success of the product may limit its life span.

1 As noted by a reviewer, fertilizer and other inputs may also have some influence on yields and costs. However, no other input information was collected in the survey. It was believed, though, that any bias from missing variables would likely be small.

2 For more information on duration analysis, interested readers are referred to the following sources: Burton, Rigby, and Young (2003); Greene (2000); Therneau and Grambsch (2000); and Allison (1995).

3 Duration analysis originated in the insurance industry where a spell was being alive and the end of the spell was death-hence the name hazard function. It is also called the force of mortality. In our application, it could be called the force of adoption.

4 An important feature of duration analysis is its ability to use incomplete data. In our study, the information that a farmer has not adopted GE soybeans up until 2000 is used to estimate the model. Such data are called "censored."

5 Here, the term "exact" refers to the nature of the estimation procedure and not to the timing of the adoption decision. If decisions did occur at precise time points, a method of estimation called "discrete" would be used.

6 The lack of dependence of the hazard ratio on the values of the other covariates is analogous to the lack of dependence of the odds ratio on the values of the other covariates in logistic regression.

7 This is analogous to the impact of the odds ratio on the probability of an event in logistic regression.

References

Allison, P. D. (1995). Survival Analysis Using the SAS System: A Practical Guide. Gary, NC: SAS Institute, Inc.

Bernard, J. C., J. D. Pesek, Jr., and C. Fan. (2004) "Delaware Farmers' Adoption of GE Soybeans in a Time of Uncertain U.S. Adoption." Agribusiness: An International Journal 20(1), 81-94.