Such action will be a response to continued weakness in the economy. Official figures next week are expected to show that real GDP grew at an annualised rate of less than 2 per cent in the third quarter, while this week's numbers showed a rise of only 148,000 in net jobs in September - and this is before the government shutdown weakened the economy.
Perhaps the starkest indicator of the fragility of the US economy, though, is the employment-population ratio. Latest figures show that only 58.6 per cent of the adult population are in work, compared with over 63 per cent before the recession. And this ratio has barely increased at all since the trough of the recession. This suggests that unemployment has fallen in part because people have dropped out of the labour market. This is consistent with the fact that wage growth - at 2.1 per cent in the last 12 months - is still low, and barely higher than inflation. "There is no sign of tightening in the labour market," says Mr Carnell.
But economists say that continuing QE might not do much to stimulate growth. James Hamilton at the University of California San Diego says $100bn of buying of Treasury bonds - the difference between an early taper and a later one - would reduce yields by no more than 0.05 percentage points. Such a small drop in borrowing costs would have little effect.
This poses the problem that printing money might do more for share prices - as investors reinvest cash from the Fed into equities - than it does for the real economy. "The US equity market is effectively rising without a corresponding increase in earnings growth," says Gary Dugan of Coutts, adding that the S&P 500 "looks expensive" on a cyclically-adjusted price-earnings ratio. In the presence of cheap money, though, expensive markets can become even more expensive.
