With the help of Jack Millman, a New York University law student specializing in tax policy and a certified public accountant, I’ve analyzed federal subsidies for higher education in every year from 1980 to the present. What follows are my findings:

The federal government is currently spending approximately $80 billion per year on subsidies for higher education—a figure that almost exactly matches the combined higher-ed spending of the 50 legislatures. These subsidies can be broken up into three basic categories: direct subsidies, tax credits, and tax breaks. (The fiscal figures cited in this analysis are adjusted for inflation in 2014 dollars.)

The most important of the direct subsidies are Pell grants, which are earmarked for low-income students. This year, the government is distributing approximately $35 billion in Pell money. The Pell grant program has expanded rapidly, more than tripling in size since 2000. It’s by far the best-known source of federal subsidies to colleges and universities.

What’s far less known outside of higher-ed circles is the remarkable extent to which the federal tax code has been amended in ways that benefit colleges and universities. According to the congressional Joint Committee on Taxation’s most recent estimates of federal tax expenditures, the IRS is currently redistributing approximately $45.7 billion annually in tax revenue in ways that directly and indirectly support American higher education. (This represents a 675 percent increase in such spending since 1990.) These subsidies can come in the form of tax credits or other types of favorable tax treatment—excluding certain forms of income from taxation or creating special deductions, for example.

The policy dynamics driving these increases are fairly straightforward: Democrats generally like to subsidize public goods such as education, and Republicans typically like tax cuts. (A number of GOP politicians have also started to champion the for-profit college industry.) Tax credits and deductions for higher education enable Congress to simultaneously pursue both of these policy preferences.

Tax credits reduce the amount of income tax an individual has to pay. Currently, taxpayers (and schools) benefit from two major programs: the Lifetime Learning Credit and the American Opportunity Credit. The former allows a taxpayer to receive a credit of up to $2,000 for qualifying higher-education expenses if the person meets a few other qualifications. The latter is a slightly more generous version of the Lifetime Learning Credit that can only be claimed for college expenses for the first four years of a student’s postsecondary education. The maximum amount taxpayers can claim via the American Opportunity Credit on their 2014 return is $2,500.

Here’s how the credits work: Suppose the Smiths pay their child’s tuition at State University (a hypothetical institution). If in 2014 the Smiths paid $2,000 or more in federal income tax and $10,000 or more in tuition charges, they would be eligible for a $2,500 refund via the American Opportunity Credit or $2,000 through the Lifetime Learning Credit.