The rebalancing of global current accounts has been hailed as a major positive development since the financial crisis. But it is in the years ahead that the adjustment will face its most difficult test.

The slumps in demand that slashed developed world deficits are now giving way to recovery. In their absence, world leaders need to find new ways to correct lingering excess surpluses in countries like Germany and China and lift export restrictions in deficit nations such as the US.

The primary cause of the 2002-08 era of exploding imbalances was currency engineering. The largest surpluses emerged in countries with strong export industries that pegged their currencies to, or kept them competitive with, the US dollar. The lasting symbol of this period is the amassed foreign exchange reserves in China, the Middle East, and parts of the emerging world.