The 1986 Tax Reform Act made mortgage interest the main deductible personal interest

Evidence

The Tax Reform Act of 1986 changed everything by making most personal interest, including interest on credit card or student loan debt or automobile loans, nondeductible. However, the act carved out an exception for mortgage interest. As long as the combined mortgages are 750,000 or less, you can deduct the interest on the mortgages for up to two different homes. (Prior to 2018, the limit was 1 million.) You are also entitled to an additional mortgage interest deduction for up to 100,000 in home equity loans if the proceeds are used to improve a home, plus a tax deduction for the state-assessed real property taxes on your home—now capped at 10,000. — Dorothy A. Brown, The Whiteness of Wealth, 182

Categorization

• DEFINE: Precise mechanics of the mortgage interest deduction carve-out — exact dollar limits and conditions.
• ADDENDUM: Direct factual mechanism for the ‘Grafting & Growth’ style of infrastructure analysis — here framed as tax infrastructure that breeds inequality.