Proponents often cite the gasoline tax as a green tax. The federal gasoline tax is currently 18.4 cents a gallon, and state taxes add an average of 20 cents more. Adjusted for inflation, gasoline tax rates have fallen to about half their rates in the 1930s (figure 1). Some economists do not consider the current gasoline tax to be a green tax, even indirectly, because over 80 percent of the revenue is used to subsidize road construction, which ultimately encourages more pollution.