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published in the 2002 State of the Nation’s Ecosystems Report as well as the 2003 and 2005 Web-Only Updates have been superseded by the 2008 Report and thus should be used with caution.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.

View Data for Agricultural Inputs per Unit of Output View Data for Agricultural Outputs

What Is This Indicator, and Why Is It Important? This indicator reports the amount of inputs used to produce one unit of output, with 1975 as the base year. So, for any input, the index value for a given year describes whether more or less of that input was used to produce a unit of output in that year than in 1975. The indicator also reports agricultural outputs over time, again compared to the output in 1975.

This is a very broad analysis. For example, all fertilizers used on U.S. farms were divided by all agricultural outputs—even if different amounts of fertilizer were used to produce each commodity. Agricultural production is driven by physical inputs and by the knowledge and skill of farmers, plant breeders, and others. A decreasing input index results because the input is used more efficiently by farmers (e.g., less fertilizer per ton of corn due to targeted application), or because of a series of advances (e.g., less labor required because of increased mechanization and more effective pesticides). Because inputs are often expensive and, like pesticides and fertilizers, may have environmental consequences, input trends are an important indicator of the long-term health of the agricultural enterprise and the level of its environmental impact.

What Do the Data Show? The output of U.S. agriculture has been increasing steadily since 1950, with total output growing by more than 60% since 1975. At the same time, farmers have used fewer inputs of energy, labor, durable goods (tractors, etc.), fertilizer, and land; since 1975, these amounts have declined by between 40 and 60%. The amount of pesticides used has increased since the 1950s, but it has remained at about the same level-about 40% over 1975 levels-since 1978.

Discussion As technology and farming practices change, inputs can change considerably. For example, a pound of pesticides today provides far more pest control than did the same amount 30 years ago. For this reason, this indicator relies upon a complex analysis of the quantities and quality of inputs used (see the technical note). A similar analysis was used for outputs, because they cannot simply be added together (a pound of strawberries is not equal to a pound of corn).

The indicator focuses on a few major, quantifiable, inputs. This means that some factors, such as changes in plant breeding (including the introduction of genetically engineered crops), are not addressed at all, and some inputs, such as water, are addressed only indirectly (in this case, through the energy costs associated with irrigation).