Comparing Itemized Tax Deductions across States: A Simple Decomposition Applied to Mortgage Interest Deductions

This paper proposes a simple multiplicative decomposition that can help in comparing the levels of mortgage interest tax deductions observed in different states or areas, and some of the reasons leading to different levels of deductions. The key parameters in the decomposition are a state’s population, its number of tax filers, the share of filers claiming a specific deduction, the average taxes paid by filers, and the average deduction among claimants. The idea is that such simple decompositions can be useful for states and local authorities to better understand some of the reasons why they may have comparatively high or low deductions in their state, and whether the levels of deductions observed are as one might have expected given their overall tax receipts.