China is not a currency manipulator, US President Donald Trump and the US Treasury Department ultimately said earlier last week. Yet the same conclusion has been reached in the past by many US economists, including former US treasury secretary Larry Summers who admitted the US government was wrong all these years in trying to push China to shore up the yuan when market forces were keeping it down.

Economists and leading currency experts such as Fred Bergsten of the Peterson Institute for International Economics and Eswar Prasad of the Brookings Institution have argued in the past that China is not manipulating its currency. And if China is doing so, it is only to prop the yuan up, not to keep it down, which incidentally does the United States a big favor by strengthening the competitiveness of its exports.

When Trump tweeted, "Why would I call China a currency manipulator when they are working with us on the North Korean problem? We will see what happens!" on Sunday, he seemed to suggest he was doing China a favor by not labeling it a currency manipulator. The fact is, the US probably owes China a thank-you note for helping prop up the yuan.