Kevin still thinks that we don't especially protect doctors, or at least not more than any other country. His key factoid is that 25 percent of our doctors were educated in foreign medical schools and then entered U.S. residency programs. He argues that this is roughly the same percentage as for other wealthy countries.

There are two important reasons why this means less than the NCAA basketball tournament scores about the issue at hand. First, we should expect many more foreign doctors would want to work in the U.S., than say in the U.K., because doctors in the U.S. earn more than twice as much as doctors in the U.K. If you're a "free trader" who has a hard time understanding this point, suppose that we paid twice as much for oil as they do anywhere else in the world. Where do we think the oil would go?

The second point is why would anyone care about the 25 percent number? I have had endless people defiantly given me this statistic as if they have shown something other than their own ignorance. What percent of our shoes comes from overseas? What percent of our clothes? Of our toys? My guess is that it would be around 70–90 percent in each category.

Suppose that just 25 percent of our consumption came from abroad in these categories because we had huge import tariffs. By the Kevin Drum standard I could say, "What do you mean we have protectionism, 25 percent of our shoes, clothes, and toys are imported."

Kevin also argues that this is an immigration issue, not a trade protection issue. Nope, it isn't. If doctors from the U.K., Germany, or India wanted to work in the construction industry, in restaurant kitchens, or as nannies for rich people, they probably would not have any problem. But they would get arrested if they worked as doctors. The issue isn't being in the U.S. or even working in the U.S., the issue is that the protectionists won't let them work in the United States as doctors.

Finally, it is worth considering the potential numbers here compared with current immigration flows. At present, we have around 1.4 million immigrants a year. Suppose we brought in 50,000 additional doctors a year for the next decade. This would be a net increase of 500,000 doctors, increasing the supply by more than 50 percent. That would hugely affect the market for doctors and likely be more than sufficient to bring their wages down to world levels.

However, this inflow of doctors would imply a net increase of immigration flows of less than 4.0 percent. If we double the number to account for immigrants of dentists, lawyers, and other currently protected professionals, we're still only talking about an increase in immigration of less than 8.0 percent. If we think that this is too many immigrants, we could reduce the flow of immigrants in other areas by an offsetting amount. 

In short, we do prop up the pay of our doctors through protectionism. We can argue whether it is good policy or not, but we can't argue that our barriers are not protectionist.