Here is the actual outcome of the policy, via the Wall Street Journal: 
 
 The ZIP Code-level analysis of Internal Revenue Service data, conducted by a team of economists for the right-leaning R Street Institute, examined how tax benefits are distributed across income levels and major metropolitan areas. The study estimates that tax preferences, particularly the mortgage-interest deduction, have helped drive up the size of houses by as much as 18% in the nation's most affluent areas while not broadly encouraging people to buy homes. Examples of better ways to help Americans with housing: build more low-income housing, give money to low-income people to get their own housing, make people with multiple homes give one of those homes to the poor.
– The tax code is rife with home ownership incentives that are both popular with voters and staunchly defended by lawmakers. But it turns out the breaks mostly just help rich people buy pricier houses, according to a new report from the right-leaning R Street Institute. They "don't encourage homeownership in any meaningful way," the study's author tells the Wall Street Journal. "People just end up buying larger homes." He estimates that in Washington, DC, the subsides have increased the average home size by 1,400 square feet. What's more, the tax breaks are mainly going to the wealthy; homeowners with incomes above $100,000 are four times as likely to claim the benefit as those earning less, because low earners rarely itemize their deductions. It's the kind of report that can anger the right and the left alike. Matt Welch at Reason calls the tax breaks an "upper class entitlement," while Hamilton Nolan at Gawker calls it a "grotesque policy outcome." Barack Obama has repeatedly called for making the benefit available only to those making less than $200,000 a year.