Heaven knows why they do it – it certainly escapes us.

Just why would Savills come up with a five-year forecast for the housing market – apart from the fact that it employs 12 (yes, 12!) people in its research team.

Savills is, of course, not alone in this kind of thing. The bigger the agent – and, usually, the more upmarket – they are, the more they do it.

But honestly, is it wise?

Regardless of how many people are in your research team, no one can see more than six months ahead.

No one knows who – if anyone – is going to win next May’s General Election.

Only yesterday, Alistair Darling described it as “too close to call”.

And if there is no winner, will it be the Lib Dems, Greens, UKIP, the Monster Raving Loony Party or – and possibly the most likely contender – the Scottish National Party that is the coalition party of choice for Labour/Conservative.

Is it really wise to try to predict anything when everything from interest rates to rent controls and mansion tax is so unknowable?

However, what should have stopped Savills in its tracks has clearly had no effect – even though it almost admits it.

There is “uncertainty in the housing market” says its latest report under the headline “Making sense of the unknown unknowns”, suggesting that even it’s 12 (yes, 12!) researchers thought that their forecasts might have a touch of the Mystic Megs and that they should have cancelled the print slot.

Indeed, one headline is “Staring into the crystal ball”.

So, just what is Savills predicting?

Well, predictably, it’s mostly very safe stuff.

Mansion tax would have a big impact on prices of very expensive properties, (no, really).

House building is an election issue (you don’t say).

Private renting among younger people is set to increase (ditto).

And if only Savills had left it there, all would be well.

Instead, it goes on to predict a 19.3% rise in house prices between now and 2019.

It even drills down regionally: London 10.4%; south-east 26.4%; south-west 21.1%; east of England 25.2%; east midlands 19.3%; west midlands 18.2%; north-east 12.6%; north-west 13.7%; Yorkshire and Humber 16.5%; Wales 15.3%; and Scotland 17.6%.

Note that all go to one decimal place. You would have thought they could be a bit more specific.

The report is fairly specific about the private rented sector, which it predicts will grow from 20% of all households to 24%.

The owner occupier share of the market would drop from 62% as of now, to 59% as of 2019. In London, Savills predict what looks like a near-collapse in home ownership, with market share going from 47% to 42%, and a rise in private renting from 30% to 39%.

On house building, Savills is sensibly restrained. It more or less says that whatever political party gets in, there won’t be enough houses built.

Easily the most interesting bit of the Savills report is that under Tony Blair, house prices grew most; and under Maggie Thatcher, there was most house building.

But of course, we still don’t know who (if anyone) will win the next General Election.

The honest forecast would run to ten letters and read: “We don’t know.”

The only flaw we can see is that it wouldn’t have taken 12 (yes 12!) researchers.

Anyway, in five years’ time and with the benefit of hindsight, we will all remember how close they got, won’t we?