The Mortgage Interest Deduction: A $30 Billion Subsidy That Benefits the Wealthy

Ask most Americans about tax breaks for homeowners and they'll nod approvingly. Homeownership is the American Dream, after all, and the mortgage interest deduction (MID) is supposed to make that dream more attainable. There's just one problem: decades of economic research show that the MID doesn't increase homeownership. It increases home prices, and it funnels the vast majority of its benefits to wealthy households who would have bought homes anyway.

The mortgage interest deduction costs the federal government approximately $30 billion per year in forgone tax revenue. That makes it one of the largest housing subsidies in the federal budget — larger than the entire budget of the Department of Housing and Urban Development. And yet, unlike direct spending programs, this subsidy operates invisibly through the tax code, shielded from the annual appropriations process and the scrutiny that comes with it.

How the Mortgage Interest Deduction Works

The MID allows homeowners who itemize their federal tax returns to deduct the interest paid on mortgage debt from their taxable income. Under current law, the deduction applies to mortgage debt up to $750,000 on a primary residence (reduced from $1 million by the 2017 Tax Cuts and Jobs Act). If you have a $500,000 mortgage at 6.5% interest and you're in the 32% tax bracket, you pay roughly $32,500 in interest in the first year and save approximately $10,400 on your taxes.

There are two critical structural features that make this deduction regressive by design:

1. You must itemize to claim it. Taxpayers who take the standard deduction — which includes the vast majority of lower- and middle-income filers — receive zero benefit. After the 2017 TCJA nearly doubled the standard deduction, even fewer households itemize.
2. The value scales with your tax bracket. A dollar of deduction is worth 37 cents to someone in the top bracket but only 12 cents to someone in the lowest bracket (who almost certainly doesn't itemize anyway). The higher your income and the more expensive your home, the larger the subsidy.

Who Actually Benefits: Follow the Money

The distribution of MID benefits is staggering in its inequality. According to data from the Congressional Joint Committee on Taxation and the Tax Policy Center, the deduction overwhelmingly flows to upper-income households.

The households earning under $50,000 — the very families most in need of help achieving homeownership — receive almost nothing from a program that costs taxpayers $30 billion annually. Meanwhile, a household with a $750,000 mortgage in a high tax bracket can receive a tax subsidy worth over $15,000 per year. This isn't a program designed to help working families buy starter homes. It's a program that subsidizes McMansions.

The Research Is Clear: The MID Doesn't Increase Homeownership

Defenders of the MID argue that it promotes homeownership — a worthy social goal with real benefits including community stability, wealth building, and civic engagement. The problem is that the evidence doesn't support this claim.

The most rigorous study on this question, published by Christian Hilber and Tracy Turner in the American Economic Review in 2014, found that the MID has no statistically significant effect on homeownership rates in most of the country. In densely regulated markets where housing supply is constrained, the deduction actually capitalizes entirely into home prices — meaning sellers raise their asking prices knowing that buyers have the deduction to offset interest costs. The subsidy doesn't help buyers; it enriches sellers.

This finding aligns with basic economic theory. In any market with constrained supply, a demand-side subsidy will be absorbed by higher prices rather than increased quantity. The MID effectively functions as a transfer payment from the federal government to existing property owners, mediated through the tax code.

"One of the great mistakes is to judge policies and programs by their intentions rather than their results." — Milton Friedman

The MID is a textbook case. Its intention is to promote homeownership. Its result is to inflate home prices, subsidize the wealthy, and leave aspiring homeowners worse off than they would be without it.

The Price Capitalization Problem

The mechanism by which the MID inflates prices is straightforward. When buyers can deduct mortgage interest, they can afford higher monthly payments, which means they can bid more for homes. In competitive markets, this additional purchasing power is quickly absorbed by higher prices. Research from the National Bureau of Economic Research estimates that the MID increases home prices by 3-6% in supply-constrained markets.

This creates a perverse dynamic: the deduction makes homes more expensive for first-time buyers who can't yet itemize (because they don't yet own a home), while providing the largest benefits to existing homeowners with expensive properties and high tax rates. It is, in effect, a regressive tax on aspiring homeowners paid to existing ones.

International Evidence: Countries That Eliminated the MID

Perhaps the most powerful evidence against the MID comes from international comparisons. Several peer countries have eliminated or dramatically curtailed their mortgage interest deductions — and homeownership rates didn't decline.

The UK's experience is particularly instructive. When Margaret Thatcher's government began phasing out mortgage interest relief at source (MIRAS) in the late 1980s, opponents predicted a homeownership collapse. It never materialized. The UK's homeownership rate remained essentially flat through the entire phase-out period. The policy's elimination had no measurable effect on ownership — exactly what economic theory would predict for a demand-side subsidy in a supply-constrained market.

The TCJA Experiment: A Natural Test Case

The United States inadvertently conducted its own experiment with the 2017 Tax Cuts and Jobs Act. The TCJA nearly doubled the standard deduction — from $6,350 to $12,000 for individuals and from $12,700 to $24,000 for married couples — making it no longer worthwhile for millions of households to itemize. The number of taxpayers claiming the MID plummeted from approximately 32 million to 13 million.

If the MID were truly essential to homeownership, we would expect to see a decline in home purchasing after 2018. Instead, homeownership rates increased from 64.2% in 2017 to 65.5% in 2020. Nearly 20 million households lost access to the MID, and the housing market didn't blink. This is as close to a controlled experiment as policy analysis gets, and the result is unambiguous: the MID is not a meaningful driver of homeownership.

Why the MID Persists: Politics Over Economics

If the evidence is so clear, why does the MID survive? The answer lies in political economy, not housing economics.

The National Association of Realtors (NAR), one of the most powerful lobbying organizations in Washington, has historically spent tens of millions of dollars annually defending the MID. The NAR's members benefit directly from higher home prices — real estate agents earn percentage-based commissions, so anything that inflates prices increases their income. The National Association of Home Builders (NAHB) similarly lobbies to preserve the deduction.

Beyond industry lobbies, the MID benefits a politically powerful constituency: existing homeowners. Roughly 65% of American households own their homes, and many believe (incorrectly, in most cases post-TCJA) that they benefit from the deduction. Proposing to eliminate a tax break that voters think helps them is political poison, even when the policy is economically indefensible.

The result is a policy that persists not because it works, but because the concentrated interests that benefit from it are better organized than the diffuse public that pays for it — a classic case of what economist Mancur Olson called the "logic of collective action."

Reform Proposals: From Tweaks to Elimination

Economists across the political spectrum have proposed alternatives to the current MID:

1. Convert to a flat tax credit. Replace the deduction with a fixed-percentage credit (e.g., 15%) available to all homeowners regardless of whether they itemize. This would extend benefits to lower-income homeowners while reducing the subsidy to high-income households. The Tax Policy Center estimates this approach could be revenue-neutral while dramatically improving distributional equity.
2. Cap the eligible mortgage amount. Reduce the cap from $750,000 to $500,000 or lower, concentrating benefits on more modest homes. This would reduce the cost of the program and limit its price-inflating effects in expensive markets.
3. Phase out over 10-15 years. Gradually reduce the deduction percentage to zero, giving markets and homeowners time to adjust. This is the approach the UK used successfully.
4. Eliminate immediately and redirect savings. Use the $30 billion in annual savings to fund supply-side housing policies — such as infrastructure grants to localities that reform zoning, or direct subsidies for housing construction.

The Free-Market Case Against the MID

From a free-market perspective, the case against the MID is overwhelming. The tax code should be neutral across asset classes. When the government subsidizes mortgage debt but not other forms of saving or investment, it distorts capital allocation, encouraging households to over-invest in housing relative to other assets like business equity, education, or retirement savings.

This distortion has macroeconomic consequences. Research suggests that the MID contributes to over-leveraging in the housing sector — the very dynamic that fueled the 2008 financial crisis. When the government subsidizes debt, people take on more of it. When that debt is secured by an asset whose price the subsidy inflates, the result is a fragile financial system built on an unstable foundation.

A tax code that treats all investment equally — that doesn't pick winners between housing, equities, bonds, or small business — would produce a more efficient allocation of capital and a more resilient economy. The MID violates this principle in favor of a politically sacred cow that has long outlived any defensible economic rationale.

The Bottom Line

The mortgage interest deduction is a $30 billion annual subsidy that fails at its stated purpose. It doesn't increase homeownership. It inflates home prices. It overwhelmingly benefits wealthy households. Countries that eliminated it saw no decline in ownership rates. And when the TCJA effectively removed 19 million households from the program, nothing happened to the housing market.

The MID persists because of political inertia and industry lobbying, not because of sound economics. Genuine housing reform — the kind that actually makes homeownership more accessible — requires directing resources toward supply-side solutions rather than demand-side subsidies that are absorbed by higher prices. Until policymakers are willing to challenge this sacred cow, taxpayers will continue funding a $30 billion program that makes housing less affordable for the very people it claims to help.