Attribution is basically the process of determining a State's on-highway gallons of motor fuel use by looking at a State's motor fuel tax data and determining if the fuel represented by the tax data is used on-highway. The outcome of the attribution process is a set of tables listing how much fuel of a specific type is used in each State and the proportion of each State's usage in comparison to the total usage for all States. The proportion of the gallons of fuel expended in a State is then used to estimate the Federal Highway Trust Fund receipts attributable to highway users in each State.

Apportionment is the distribution of funds to the States by statutory formula. Certain factors in the apportionment formulas of four major highway programs are based on the attribution tables.

Attribution Overview

Attribution starts when Federal revenue is collected by IRS and assigned to the appropriate tax category ­ i.e., gasoline, gasohol, diesel and special fuels, tire tax, truck-tractor and trailer retail excise tax, and heavy vehicle-use tax. The total funds in each tax category are verified and reported by IRS; however, IRS has no record of where or how the fuel was consumed. Therefore, FHWA uses the attribution process to determine on-highway fuel use within each State. FHWA uses State-reported data and also statistical methods to estimate missing or not-reported State data.

The validity of the attribution process is dependent on receiving accurate data from the States. Typically State revenue departments maintain records according to the legislative requirements of that State. For example, some fuels may be exempted from tax, or taxes may be refunded, or the tax rate for a particular fuel may vary depending on the fuel's use. In some States, these data do not exist, and FHWA must estimate the data.



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