In the second of a series of papers discussing the impact of biotechnology on U.S. average crop yields, an Ohio State University agricultural economist said biotechnology might be just one factor contributing to reduced yield variation.

"While this study certainly doesn't preclude biotechnology as an explanation for the decline in the variability of average yields for corn, cotton and soybeans, it does suggest more universal factors are likely occurring," said Carl Zulauf, a professor with the Department of Agricultural, Environmental and Development Economics and the Ohio Agricultural Research and Development Center.

Zulauf compared the variation from trendline yields during two periods. The first period, 1940-1995, started when average U.S. yield for the 14 crops studied generally began improving. The comparison period, 1996-2011, marked the years when biotech seeds were commercially available in corn, soybeans and cotton, which were three of the 14 crops included in the study.

He explained that the objective of the study was to provide information concerning the commonly expressed argument that biotechnology has reduced yield variability.

"A decline in yield variability is a universal characteristic of the U.S. crops included in this study," Zulauf concluded. "It is not just a characteristic of the biotech crops. Moreover, little difference appears to exist in the size of the decline in yield variability across biotech and non-biotech crops."

The study found that for all 14 crops, the variation from trendline yield was lower during the recent 1996-2011 period than during the earlier 1940-1955 period. The average decline in yield variation for all 14 crops was 45 percent. The average decline for the three biotech crops studied was 43 percent, compared with 45 percent for the 11 non-biotech crops.

Zulauf said that because the decline in yield variability was a common characteristic, it is likely that universal factors are involved. He said one universal factor could be that both biotech and traditional breeding methods have been equally successful at creating varieties that reduce yield variation. A second factor could be that weather was simply more favorable across the major U.S. production regions during 1996-2011 than during 1940-1995.

He also pointed out that "regardless of the factors at work, a more reliable supply reduces the size of stocks that need to be carried to assure an adequate supply of food before the next harvest, thus reducing the cost of food. A more reliable supply also enhances the ability to expand non-food uses of crops, such as energy production."

Zulauf's paper on biotechnology and crop yield variation can be found online at http://aede.osu.edu/biotechnology-and-variation-average-us-yields , along with his previous paper on biotechnology and crop yield trends ( http://aede.osu.edu/biotechnology-and-us-crop-yield-trends ). These papers contain a more complete discussion of the methodology.