Just what the G20 needed to keep things lively: unequivocal evidence of vast and persistent imbalances. The latest monthly data from China confirmed another big annual leap in exports and a whopping trade surplus of $27bn, two-fifths wider than the 2006-2009 average. Thursday’s industrial production (expected to be strong) and consumer price inflation numbers (probably above target) should strengthen the critics’ conviction that China’s currency is weaker than it should be.

For peacemakers at the Seoul summit, the good news is that China has abandoned its attempts to persuade the world that the red-back is fairly valued. Since mid-June, when the People’s Bank said it would allow more foreign exchange flexibility, appreciation has been a matter of when, rather than if. The bad news is that the principals are still at cross-purposes. While Beijing wants to lift purchasing power through increased wages and subdued inflation, and appears ready to tighten monetary policy to do it, Washington just wants a stronger renminbi against the dollar. China, in short, is focusing on real appreciation; the US nominal.

The dollar/renminbi rate has become a political plaything. Note, for example, that this week’s surge before the Seoul summit accounts for a quarter of the renminbi’s total strengthening since mid-June.