A single-stage commodity tax (i.e. a tax levied on a commodity only once as it passes through the production process to the final consumer). An excise tax is narrowly based; enabling legislation specifies precisely which products are taxed, as well as the tax rate. Sales taxes are more broadly based; their tax base comprises many commodities and legislation designates those commodities not subject to tax. Excise taxes are commonly assessed on automobiles, cigarettes, liquor or gasoline. They are sometimes levied in hopes of discouraging the use of the product taxed. Revenues from such taxes may also be set aside from general revenues and used for some purpose related to the taxed product. For example, an excise tax on cigarettes might discourage smoking by raising its cost and revenues from it might be used to fund cancer screening programs.