Behind this decision, however, is an even bigger issue: is ultra-cheap money really necessary to maintain growth in the world economy, and might it even be verging on the counter-productive?
Hardly anyone doubted whether we needed a monetary stimulus to jack up the world economy after the financial crash of 2008/9. But it is much harder to justify it after several years of expansion, particularly given the impact cheap money has had on asset values, such as housing, in the UK.
The argument is rather similar to that concerning expansionary fiscal policy. In the extreme situation of six years ago, few people objected to a temporary rise in fiscal deficits — whatever views they took of fiscal policy in the previous years.
But since then the narrowing of deficits in the US, here in the UK or indeed in Germany, does not seem to have damaged growth as much as pessimists had expected, indeed maybe not at all.
It would be nice to have historical evidence of what happens when interest rates are increased from near-zero levels so that we could gauge what might happen in the months ahead.
But we haven’t, for the simple reason that rates have never been as low as they are now for such a long period before. We are flying blind.
"We need people to save for their old age but we punish them when they do."
<p>Hamish McRae</p>
What we can observe, however, is that the country with a longest experience of very low rates, Japan, has had 25 years of recession or minimal growth.
There are other reasons for this, including demography, but the experience does at least show that ultra-cheap money does not of itself boost growth if the other conditions for growth are absent.
Ultra-loose fiscal policy has not helped much either, come to think of it.
We can also see some of the disadvantages of cheap money. It has not led to a surge in inflation, as many predicted, but it has led to asset inflation, which has increased wealth inequality just about everywhere.
If asset values shoot up, the people who own the most assets gain at the expense of those who don’t, and you can make a good argument that wealth inequality is more socially divisive than income inequality.
There are other downsides to ultra-low interest rates, including the impact on availability of credit — yes, money is cheap but you can’t get it — and the social impact on savers in a period of rapid ageing of the population.
We need people to save for their old age but we punish them when they do. Further, the more sophisticated the savers, the better they can get round low rates; it is the unsophisticated (and probably poorest) who are hardest hit.
However, listing disadvantages of cheap money does not answer the question: what happens when it ends?
Until recently, the prevailing view among central bankers and economists was that we should be alarmed.
Highly indebted societies could not stand a sharp increase in interest rates. If taken to extremes, that must, of course, be true.
If mortgage rates went to 7%, there would be a lot of people who would lose their home.
But in recent months the view seems to have shifted a bit, to a position that a modest increase in rates might actually boost confidence.
Everyone knows rates must rise some time, and can anticipate that by, for example, getting a fix on their mortgage.
For the Fed to move this week would end an uncertainty, which would be positive, and might reduce the need for sharper increases next year.
