I think the lesson is, you can borrow when times aren't so good and cyclical factors will help get you out of it."

Cyclical factors, such as government stimulus or austerity policies, cause the actual unemployment rate to vary around the natural rate.

Roughly half of this decline can be attributed to cyclical factors and half to long-term trend factors.

A. I don't think a slowing economy will affect Amazon, whether it is done by the Fed or by cyclical factors.

BESIDES these cyclical factors, some investors say, the mind-set has changed among producers of metal and many other commodities.

But, as the Congressional Budget Office has noted, there are a variety of reasons for that, including the cost of malpractice awards, decreases in the investment income of insurance companies and cyclical factors in the insurance market.

The Congressional Budget Office estimates this year's structural budget deficit - what the deficit would be if cyclical factors like a depressed economy went away - at 3.9 percent of G.D.P. That's almost twice the average during the past 20 years.

But if you look at where interest rates are, at the fact that these economies are recovering and at structural and cyclical factors, there is every reason to believe Europe could have an extended period of expansion the way we have in the United States."

I hope that it is something more, but we must also tell the European citizens that we must carry on working because the rationalisation of public finances we saw last year may also be due to cyclical factors and not to deliberate or structural decisions.

But there is a risk for politicians, warns Harris, who make big promises to cut crime, but are hostage to cyclical factors such as an economic downturn, or new gadgets driving up robbery, which neither they or police chiefs can control: "Boris takes over the Met and he is responsible for whatever happens, whether it is good or bad."