This chart shows the trend in U.S. greenhouse gas emissions as a total of all gases, in total teragrams of carbon dioxide equivalents for six economic sectors from 1990 to 2006. The six sectors represented in the line graph are residential, commercial, industry, transportation, electricity generation, and agriculture. The x axis represents one-year increments from 1990-2006. The y axis represents teragrams of carbon dioxide equivalents in 500 teragram equivalents, ranging from zero to 2,500. The graph shows that electricity generation accounted for the largest portion (34 percent) of U.S. greenhouse gas emissions in 2006. Transportation activities, in aggregate, accounted for the second largest portion (28 percent).