The G20 has been in existence for years but achieved little. The November meeting sketched out a grand plan to co-operate in supporting global growth and combating the financial crisis – recognising the falsity of vague hopes that big parts of the world economy would be “decoupled” from the slowdown.

Yet within a month, its only concrete plan had been shattered. As a signal of its determination to avoid 1930s-style protectionism, the G20 pushed for an outline agreement in the so-called Doha round of trade talks before year-end and pledged to refrain from new protectionist measures for 12 months. The former once again failed to materialise, with the US and the big emerging markets, notably India, failing to shift from entrenched positions. And the no-protectionism pledge lasted less than 48 hours before Russia announced its intention to raise car tariffs. The promise has since been violated further by India, Indonesia, Brazil and Argentina. A quarter of the G20 broke its word within a month. This is not the way to build credibility.

The G20's fundamental problem is that it has done little to change incentives. Global governance is not a game of Sudoku. Anyone can sit down with a matrix of financial statistics, conjure up a new list of systemically significant economies and convene a festival of hand-wringing. But to transform such a body into a governing mechanism requires making its decisions materially affect the domestic debate in each of its signatory countries.