Nationwide

You need a mathematics degree and a brain like Einstein to work out exactly how the house price indices are put together – most of us struggle even to work out why something like house prices are ‘seasonally adjusted’ as we hear so often when the figures are quoted.

The providers say this has to be done to iron out natural changes in prices that happen every year and don’t reflect any broader trends. In the spring and autumn, for example, a traditional increase in buyers mean prices tend to edge up, even though the overall trend may be flat or even falling. Seasonal adjustment means we aren’t misled by these factors, apparently. Though you will probably get a headache if you ask any of the statisticians any more about their methods.

You might also get a headache if you ask about the way the figures are altered to ensure they cover the whole country – a form of regional, rather than seasonal adjustment. Nationwide was one of the first to introduce this form of re-calculation because it didn’t want its figures to be biased by the fact that most of its data used to come from branches in the south of the country. Regional adjustments apparently balance this out and ensure that the north and all the other regions are properly represented in the figures.