The choice of the personal income tax base

We find that the choice to tax couples based on their joint income, and the inclusion of dividends, interest income, and dependents' deduction in the tax base in roughly their current form can be rationalized simply based on their value in better approximating an ability tax, without any need for supplementary motivations for these provisions. However, the inclusion of mortgage and property tax payments in the list of itemized deductions cannot be defended on these grounds.