The Chinese refuse to acknowledge the problem. Recently Wen Jiabao, the prime minister, dismissed foreign complaints: “On one hand, you are asking for the yuan to appreciate, and on the other hand, you are taking all kinds of protectionist measures.” Indeed: other countries are taking (modest) protectionist measures precisely because China refuses to let its currency rise. And more such measures are entirely appropriate.

Or are they? I usually hear two reasons for not confronting China over its policies. Neither holds water.

First, there’s the claim that we can’t confront the Chinese because they would wreak havoc with the U.S. economy by dumping their hoard of dollars. This is all wrong, and not just because in so doing the Chinese would inflict large losses on themselves. The larger point is that the same forces that make Chinese mercantilism so damaging right now also mean that China has little or no financial leverage.

Again, right now the world is awash in cheap money. So if China were to start selling dollars, there’s no reason to think it would significantly raise U.S. interest rates. It would probably weaken the dollar against other currencies  but that would be good, not bad, for U.S. competitiveness and employment. So if the Chinese do dump dollars, we should send them a thank-you note.

Second, there’s the claim that protectionism is always a bad thing, in any circumstances. If that’s what you believe, however, you learned Econ 101 from the wrong people  because when unemployment is high and the government can’t restore full employment, the usual rules don’t apply.

Let me quote from a classic paper by the late Paul Samuelson, who more or less created modern economics: “With employment less than full ... all the debunked mercantilistic arguments”  that is, claims that nations who subsidize their exports effectively steal jobs from other countries  “turn out to be valid.” He then went on to argue that persistently misaligned exchange rates create “genuine problems for free-trade apologetics.” The best answer to these problems is getting exchange rates back to where they ought to be. But that’s exactly what China is refusing to let happen.

The bottom line is that Chinese mercantilism is a growing problem, and the victims of that mercantilism have little to lose from a trade confrontation. So I’d urge China’s government to reconsider its stubbornness. Otherwise, the very mild protectionism it’s currently complaining about will be the start of something much bigger.