Over the past half century, globalization and automation have pushed America's GDP higher and higher, but the gains haven't been distributed equally. Economic disruption has left behind manufacturing communities in the rust belt, leading some politicians on the right to question open, free market economics. We should build walls — physical and metaphorical — to protect American jobs, they say. But today I'm joined by Glenn Hubbard, who prefers economic bridges to opportunity over walls.

Glenn is a nonresident senior fellow at the American Enterprise Institute. He is also Dean Emeritus of Columbia Business School and author of "The Wall and the Bridge: Fear and Opportunity in Disruption's Wake," released earlier this year.