Lawrence Summers was secretary of the Treasury under Bill Clinton and director of the National Economic Council under Barack Obama.​Thus, many of the policies he helped enact are now being reversed or assailed​by President Donald Trump.

Mr. Summers shared his views on current economic policies with Greg Ip, The Wall Street Journal’s chief economics commentator. Edited excerpts follow.

MR. IP: You played a part in Nafta, the World Trade Organization, the Korea-U.S. trade agreement and the Trans-Pacific Partnership. We now have a president and an administration who believe that all those things were terrible mistakes, that the U.S. has been a loser as a result of free trade. Are they wrong?

MR. SUMMERS: They’re wrong because each of those were good deals. If you looked at how much trade barriers in the U.S. were reduced, and at how much trade barriers in the other countries were reduced, in every case they were reduced two, three, four, five times as much in the other countries as in the U.S.

The main thing these trade agreements have done is to open other markets to our businesses and to our exports. You don’t have to get into abstractions of free trade. If you just look at it as mercantilism, we’re tearing down their barriers lots more than we’re reducing any of our barriers, mostly because we didn’t have any barriers to start with.