Tensions are rising over Chinese economic policy, and rightly so: China’s policy of keeping its currency, the renminbi, undervalued has become a significant drag on global economic recovery. Something must be done.

To give you a sense of the problem: Widespread complaints that China was manipulating its currency  selling renminbi and buying foreign currencies, so as to keep the renminbi weak and China’s exports artificially competitive  began around 2003. At that point China was adding about $10 billion a month to its reserves, and in 2003 it ran an overall surplus on its current account  a broad measure of the trade balance  of $46 billion.

Today, China is adding more than $30 billion a month to its $2.4 trillion hoard of reserves. The International Monetary Fund expects China to have a 2010 current surplus of more than $450 billion  10 times the 2003 figure. This is the most distortionary exchange rate policy any major nation has ever followed.

And it’s a policy that seriously damages the rest of the world. Most of the world’s large economies are stuck in a liquidity trap  deeply depressed, but unable to generate a recovery by cutting interest rates because the relevant rates are already near zero. China, by engineering an unwarranted trade surplus, is in effect imposing an anti-stimulus on these economies, which they can’t offset.