In a recent piece I discussed some of the evidence that American workers have been hurt by free trade since China joined the World Trade Organization in 2000. I criticized economists for presenting a far too glib and confident public case for free trade when scholarly research has begun to show a more mixed picture.

But that still leaves an enormous question unanswered. What policy steps could the U.S. and other industrialized countries have taken to blunt the worst effects of trade with China? Did policy makers err, or was China's entry into the global trading system simply an unforeseen negative shock to U.S. workers, like a hurricane or volcano? What might have been done differently?

One thing the U.S. could have done — had Europe and Japan helped — is to block China from entering the global trading system. The developed nations, had they so chosen, could have shut China out of the WTO and arranged systems of tariffs to keep Chinese goods out of their markets.