…the fractional assessment of homes was easily the largest single government housing subsidy in the postwar era, and it was among the largest categories of social expenditure of any kind, direct or indirect. Fractional assessment of residential property provided a subsidy that was forty times greater than federal spending for public housing. It was ten times greater than the home mortgage interest deduction. It was five times as costly as more controversial "welfare" programs like Aid to Families with Dependent Children. Although fractional assessment did not show up on official government budgets, on the eve of the tax revolt it was providing more benefits than any other social policy in America except for the twin blockbusters of the federal budget, Social Security and Medicare.
That is from the new book The Permanent Tax Revolt: How the Property Tax Transformed American Politics, by Isaac Martin. The main thesis of this book is overstated, namely that the professionalization of property tax assessments is the root cause of American exceptionalism on tax politics; nonetheless I found this a very informative and stimulating read.