The California Legislative Analyst’s Office has prepared a report on Tax Expenditure Reviews.  Here is the abstract:

Tax expenditure programs (TEPs) are features of the tax code—including credits, deductions, exclusions, and exemptions—that enable a targeted set of taxpayers to reduce their taxes relative to what they would pay under a “basic” tax-law structure. The state’s TEPs number in the hundreds and are valued in the tens of billions of dollars annually, and are used mostly to encourage certain types of behavior or provide financial assistance to taxpayers. This report provides information on newly enacted TEPs and reviews selected existing TEPs as to their effectiveness and efficiency. One of these is the mortgage interest deduction, valued at about $5 billion yearly. This program is found to be an inefficient means of promoting home ownership, and options are offered for improving it, including capping the deduction amount or replacing it with a targeted tax credit.

The discussion of Clifornia’s mortgage interest deduction at pages 15-35 is particularly interesting.  Check out four of the many interesting charts and tables below the fold: