A US downturn will not be avoided. US households cannot continue to spend more than their income as they have in recent years, even if the credit crunch eases. Household consumption is bound to fall steeply. The writedowns in US household wealth from the reversals in housing and equities will probably reach $15,000bn (€12,000bn, ￡9,700bn) and the resulting steep decline in private consumption and investment could reach about one-tenth of that amount.

Some other economies will also suffer home-grown recessions because they too allowed a housing bubble to develop, which has now burst. This appears to be the case in Australia, the UK, Ireland and perhaps Spain. This drop in spending outside the US because of capital losses and reversals in housing may add another $300bn-$500bn to first-round decline in global demand.

Yet even a steep recession in the US and in a few other countries need not throw the world into recession. The world economy is about $60,000bn, so a first-round demand decline of as much as $1,800bn would be about 3 per cent of world output. If there were no offsetting macroeconomic policy changes, the demand decline could be multiplied further to as much as 6 per cent, relative to 4 per cent trend growth, meaning a global decline of about 2 per cent.