The Federal government incurs a cost for every item that is deductible in the computation of taxable income. These costs, which take the form of forgone tax revenue, are often referred to as "tax expenditures." The Joint Committee on Taxation regularly estimates the current and projected tax expenditures associated with of a long list of provisions in the tax law. Locate the Joint Committee on Taxation's most recent analysis, and identify the current tax expenditure associated with the deductions for medical expenses, interest on student loans, mortgage interest, and charitable contributions. How are these costs expected to change over the next five years? How is the concept of tax expenditures helpful to tax policy analysts and lawmakers?