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House price index methodology

Nationwide house prices are mix adjusted - i.e. we track a representative house price over time rather than the simple average price. We do not use the simple average price because it is too easily influenced by a change in the mix (i.e. proportion of different property types, locations etc) of houses.

Although it remains similar to the Halifax method we substantially updated our system in 1993 following the publication of the 1991 census data. These improvements mean that our system is more robust to lower sample sizes because it better identifies and tracks our representative house price.

To find out how we create our House Price Index, view the full methodology (PDF).

Questions and Answers

What data is the index based on?

House price information is derived from Nationwide lending data for properties at the post survey approval stage.

How long have you been publishing house price data?

We have the longest unbroken run of house price data - it stretches back to 1952 on a quarterly basis and 1991 on a monthly basis

Are your house prices biased because you do more lending in the South East?

No. The whole point of mix adjusting prices is to remove any bias that the Nationwide mortgage data may exhibit whether that be the type of property we lent on or its location or indeed any one of the other characteristics we use to identify our representative house.

What sample size do we have?

Nationwide has sufficient sample size to produce a representative house price series. N.B. Net lending figures quoted at our half yearly and annual results are not a guide to our sample size. Sample size is based on the number of new loans we write i.e. the amount of gross lending for house purchase

Why are Nationwide's house prices different to Halifax's?

Over long periods the Halifax and Nationwide series of house prices tend to follow similar patterns. This stems from both Nationwide and Halifax using similar statistical techniques to produce their prices. Our average price differs because the representative property we track is different in make up to that of Halifax.

What is seasonal adjustment?

We seasonally adjust our prices because the time of year has some influence. Winter months tend to see weaker price rises and spring/summer see higher increases all other things being equal

Where can I find out what region my property is in?

Click the what region are you in? link on the HPI calculator to use our postcode search. Alternatively, view a list of all local authorities and their associated house price region (.xls)

Did you know...

Nationwide have been publishing house price data since 1952.

Legal Information

The Nationwide House Price Indices are prepared from information that we believe is collated with care, but no representation is made as to their accuracy or completeness. We reserve the right to vary our methodology and to edit or discontinue the indices at any time, for regulatory or other reasons. Persons seeking to place reliance on the indices for their own or third party commercial purposes do so at their own risk.

All changes are nominal and do not allow for inflation.