For much of past year, Ben Bernanke’s activist US Federal Reserve was ahead of the curve, making bold use of the experimental monetary instruments he had conceived as an academic. Across the Atlantic, Jean-Claude Trichet’s European Central Bank was behind the curve – active, but not active enough relative to the crisis it faced. Today’s big question for the world economy can be framed this way: might these roles be reversed?

The European part of this pivot is already half complete. After months of political argument about the details of an emergency liquidity fund worth €440bn, the central bank lost patience and, under the new leadership of Mario Draghi, injected more than twice that into Europe’s banking system. The acronym-strewn arcana of firewall diplomacy were abruptly bypassed. Who cares about negotiations for a bailout fund when the central bank can print one?

Mr Draghi’s intervention solved the acute part of Europe’s problem. What is less well recognised is that the ECB’s new activism could also, if extended, address its chronic ailments. Europe’s periphery remains hobbled by too much debt and too little competitiveness. But if the ECB has the guts to engineer a sustained period of monetary ease – and grit its teeth as German inflation inches up – it can deliver debt relief by the back door and competitiveness via a weaker euro. Rather than waiting for arduous labour reform to make Spanish workers competitive with Germans, a determined ECB could help Spain compete with Thais or Canadians. Mr Draghi has not yet revealed himself to be ready for this further step; but he has already shown a capacity to be radical.