• 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 (Land Registry uses this method) 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

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 our house prices different to the 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

Full Methodology