Aquarius: You will get a 3.6% pay rise but have to fork out £849 for your car’s MOT

Hopi bemoans the lamentable accuracy of economic forecasts, asking:

Why do governments bother making such definitive predictions of the future? Why not adopt a system of range forecasting, where we work within assumptions of probability of different outcomes?

And Chris suggests how this might look in practice:

So, if we assume that the £173bn forecast for PSNB in 2010-11 is the central point of the projection, a range forecast would take the form of saying something like:
There’s a roughly two-thirds chance PSNB will be within the range £143-£203bn, and a one-in-six chance it will be below this, and a one-in-six chance it’ll be above it.
It would, however, be impossible for a government to do this.
Every know-nothing numbskull and opportunist would claim that this is not what it is - a sensible recognition of the fact that the economic future is inherently unpredictable - but rather a confession of ignorance.

And he explains why politicians keep putting out such falsely precise figures:

One of the most important images is the illusion that they are "in charge", which requires that they deny the existence of uncertainty.

The thing is, though, that nobody believes official forecasts of GDP, spending, tax, debt, inflation, unemployment and so on. Nobody.

So, if maintaining the illusion of certainty is impossible, what role do these forecasts serve?

I think their main purpose is as media fodder. A specific number is much easier to communicate than a probability distribution, and for the media reporting a prediction, it does show that they know things in detail. A forecast of 2.5% growth may be disbelieved, it may turn out to be laughably wrong, but it can be reported with confident precision. ‘We know our stuff, because our stuff is simply what other people say, whether or not they know their stuff.’

It also allows for much more pointed challenges to be put to politicians: ‘Where are you going to find the extra £8.2 billion?’ seems a penetrating question that ought to require a detailed answer, but of course no credible detailed answers can be given, so the politician gets made to look a knave or a fool. The debate then gets conducted within the safe confines of a recorded and definite narrative, rather than out in the real world, where informed questions require you to know a lot more – including the limits of your own knowledge.

Which means that the reason politicians keep doing this is that they hope their own set of guesstimates will get picked up and used in questions to needle the other lot.

Oh, how edifying. Another way in which the news media and the political parties are symbiotic upon each other, and jointly parasitic upon the rest of us.