What are the economic effects of earmarking the revenues from a tax to a particular expenditure programme? More precisely, is economic efficiency enhanced or diminished by dedicating a tax to a specified government purpose, such as education, highway construction, or medical research? Any attempt to determine the efficiency implications of tax earmarking requires some model, either implicit or explicit, of the political process. By imposing an additional constraint on government, tax earmarking can affect government decisions on not only how to spend tax revenues, but on how much tax revenue to raise.