Note that the data published in the 2002 State of the Nation’s Ecosystems Report as well as the 2003 and 2005 Web-Only Updates have been superseded by the 2008 Report and thus should be used with caution. For the most recent data, purchase the 2008 Report from Island Press.

The Data

Data Source: Data are from the U.S. Department of Agriculture National Agricultural Statistics Service (NASS).

Data Collection Methodology: State offices collect and estimate crop yield data from sample surveys of farmers and their business associates (farm service agencies, cotton gins, marketing associates). NASS obtains the yield estimates, which are verified and analyzed on a national level. Survey data are supplemented by information from the Census of Agriculture, which is carried out every 5 years.

Data Manipulation: Yields, which are generally reported as bushels per acre for corn, soybeans, and wheat, and as tons per acre for hay and cotton, were divided by their respective value for 1975. Thus, values above 1.0 indicate higher yields than in 1975, and values lower than 1.0 indicate lower yields than in 1975.

Data Access: Data can be downloaded from “Quick Stats” available on the NASS web site (http://www.nass.usda.gov/index.asp ). Note that “corn” refers to corn for grain only and does not include corn for silage.

2003 Web Site Update: Data for 2001 and 2002 were downloaded from the Quick Stats Website as listed under Data Access.

2005 Web Site Update: Data for 2003 and 2004 were downloaded from the Quick Stats web site as listed under Data Access.