For those households, by the center’s calculations, the tax benefit of the deduction amounts to about 1.5 percent of after-tax income. By way of comparison, the value to households earning $40,000 to $50,000 is closer to 0.3 percent of after-tax income; for households earning $50,000 and $75,000, it is 0.7 percent.

Why is this so? One reason is simply that people who have more money are more likely to have expensive homes and bigger mortgages. They may also have second homes, and under the current rules, mortgage interest may be deducted on those as well, up to a cap of $1 million in debt.

The other factor is that the value of the subsidy increases along with your tax bracket.

For households in the 15 percent bracket, the tax benefit for every $1,000 of mortgage interest deducted is $150. That benefit rises to $350 for households in the 35 percent tax bracket.

Robert Dietz, an economist for the National Association of Home Builders, which opposes cuts in the deduction, points out that households earning up to $200,000 could still be considered middle class in some parts of the country. Taxpayers who benefit the most from the mortgage deduction tend to be concentrated in high-cost metropolitan areas. So although their income levels sound high relative to the rest of the nation’s, the incomes reflect a higher cost of living.

He also notes that much of the tax benefit is going to younger homeowners who are at the beginning of their mortgages, when interest charges are highest. “The largest mortgage interest deduction average was found for those ages 35 to 45 years,” he said.