In its recent document release entitled, "2008 Energy Balance for the Corn-Ethanol Industry", the United States Department of Agriculture updated its energy-balance calculations for corn ethanol. The calculation-update corrects for the 20% decline in energy related nitrogen use since the mid- 1990s, and a 50% decline in direct energy components (also since the mid- 1990s) for the cultivation of the corn feedstock. Overall, the decline in nitrogen use and other direct energy components reduced the energy requirement for the production of a bushel of corn by about 50%. "The ratio is about 2.3 BTU (British Thermal Units, a unit of energy) of ethanol for 1 BTU of ethanol inputs, when a portion to total energy input is allocated to by-product and fossil fuel." The corn energy input to ethanol production reportedly declined to 9,811 BTU/gal from 16,346 over the most recent 10-year period.