The intellectual impact of the crisis has already been colossal. The “Greenspanist” doctrine in monetary policy is in retreat. It no longer seems clear that it is easier for central banks to clean up after asset price bubbles burst than to prick them when they are small. Monetary authorities will need to be more concerned both about financial stability and global imbalances which allowed a few countries to build up vast surpluses while a few others ran yawning deficits.

Finance has already changed irrevocably. The grand investment banks which once strode alone have either collapsed, or joined the flock of retail banks. Governments are now borrowers, lenders, investors and insurers of last resort for much of the financial system. The future of finance will be determined by their efforts to disentangle themselves from the thickets of guarantees they have been forced to make. The depth of the crisis will determine how easily they manage it.

The fiscal cost of this episode is unclear. In some countries, they may be state-busting. Some nations will need to cope with extraordinary fiscal tightenings in the coming years. The domestic impact of government spending – and its geopolitical ramifications – could yet be colossal. Again, much depends on how soon the downturn ends.