most consumer goods have posted prices that exclude tax; taxes are added based on a percentage of the purchase price. because of primitive gasoline pumps in the 1920s, united states gasoline prices are posted with taxes included and the taxes are set on cents per gallon. taxes are added by federal, state and local governments. (these taxes collect the cost of maintaining the roads.) as of 2009, the federal tax is 18.4¢ per gallon for gasoline and 24.4¢ per gallon for diesel (excluding red diesel). among states, the highest gasoline tax rates, as of january 2011, are california (47.7¢/gal), new york (47.3¢/gal), hawaii (45.8¢/gal), and connecticut (45.2¢/gal). the federal government and many states fail to increase their gasoline taxes over time with inflation. however, some states also charge a sales tax as a percentage and vary in amount depending on the cost of the gasoline.