It’s significant that Trump gave his big anti-trade speech in the Pittsburgh area. That part of Western Pennsylvania illustrates in a very concrete way how the open/closed debate will play out.

Pittsburgh is a great renaissance story. I recently got a tour of it from the mayor, Bill Peduto. We visited a beautiful, tight Italian community with family-owned businesses stretching back generations. We visited a resurging African-American community where local activists were building a cultural center in the home of the great playwright August Wilson. Mostly we just saw acres and acres of new development: new restaurants, new museums, new loft-style office spaces and several gleaming new hospitals.

Pittsburgh has come so far from the deindustrialization days of the 1970s and 1980s.

But then I drove through the steel mill towns along the Monongahela and other rivers. The storefronts and banks were boarded up, the downtowns deserted. The mills are still operating, but they are so efficient they’re eerily empty of human presence. The towns still have residents, but not much is going on. I drove for miles, unable to find even a diner for lunch.

It occurred to me the Pittsburgh renaissance didn’t really grow up out of the metro Pittsburgh of old. Instead one Carnegie-Mellon type layer of prosperity and innovation had grown on top of the old working-class layer, which was still there and in bad shape.

When you’re in the top layer you see why free trade is so good. Living standards are rising. A study by the Peterson Institute found that past trade liberalization laws added between $7,100 to 12,900 in additional income to the average household. A study by Peter Petri and Michael Plummer estimates that the Trans-Pacific Partnership, which Trump opposes and Clinton sort of opposes, would boost American incomes by $131 billion.

You also see how an efficient manufacturing sector makes it possible to divert resources into things that improve the quality of life. As Neil Irwin pointed out in The Times, Pittsburgh has lost 5,100 steel jobs since 1990. But it has also gained 66,000 health care jobs over the same time.