The mortgage interest deduction costs the U.S. Treasury roughly $50 billion a year in lost revenue. It’s number I’ve heard from different lobbyists in the mortgage industry and I’m not sure if it’s accurate. But it may not matter when you ask this basic question: how much does housing construction, home ownership and all the ancillaries that come along with those two add to the U.S. economy? Traditionally, Republicans have not been fans of housing, wanting to remove subsidies for homeownership, including the dismantling of Fannie Mae and Freddie Mac. Keep in mind that the GOP has disliked the GSEs for at least two decades, though there have been exceptions to the rule. As the presidential debates begin this week, housing and mortgage professionals should pay close attention to what the candidates say regarding federal housing subsidies. Just how much do these two men really understand?