Last summer, Motley Fool columnist Morgan Housel wrote that the deductibility of mortgage interest would lower tax revenue "by $1.4 trillion over the next decade." Removing the deduction would make home prices more affordable and would also discourage Americans from levering up to buy property.

And yet, very few people favor removing the deduction.

In late March, Robert Shiller stopped by Motley Fool Headquarters for an hour-long interview about home prices, stocks, bubbles, and more. A Yale professor who just published his 10th book, Finance and the Good Society, Shiller is the co-creator of the S&P Case-Shiller Home Price Index and is an expert on U.S. housing.

In the video below, I ask Shiller for his thoughts on the mortgage interest deduction. See what he thinks it's good for, and who he thinks should benefit from some governmental subsidy. (Run time is 1:10; a transcript is below.)