Mix-adjusted
A mix-adjusted price allows for the types of homes sold each month, so the figure does not move just because more flats or large houses sold.
A mix-adjusted price or index allows for the kind of homes that sold in each period. It measures how the price of a similar set of homes has changed, rather than how the prices of whatever happened to sell have changed.
The House Price Index is mix-adjusted. Simple figures such as a median price or a mean are not.
The problem it solves
The homes that sell in one month are never the same set as those that sold the month before. In some months more flats sell, in others more detached houses. A simple median or average price moves with that mix, even when no home has changed in value.
As an example, suppose a district sells mostly flats in one quarter and mostly family houses the next. The median could jump by a large amount between the two quarters while the value of each home stays the same. The example is only for illustration.
How the adjustment works
The UK House Price Index uses a method called hedonic regression. It looks at the features of each home sold, such as its property type, size and location, and estimates how much each feature adds to the price. It then works out what a fixed, typical set of homes would have sold for in each month.
Because the set of homes is held steady, the change in the index reflects price movement rather than a shift in what was sold.
Doing a simple version yourself
You do not need a statistical model to allow for mix in a rough way. Compare one property type at a time, keep new builds separate from older homes, and compare freehold houses with freehold houses and leasehold flats with leasehold flats.
Price Paid Data records each of these details, so the split is easy to make. Our guide to working out house price change shows how, and comparing streets and postcodes covers fair comparisons between areas.
Mix-adjusted and local medians
A mix-adjusted index and a local median answer different questions. The index tracks how prices are moving for a typical set of homes across a wider area. A median tells you the middle price of the homes that actually sold in a particular place. Both are useful, and their figures will not match.
| Allows for | Property type, size and location |
| Used by | UK House Price Index |
| Method | Hedonic regression |
| Not mix-adjusted | Simple medians and means |
Related terms
House Price Index · Median price · Average price · Property type · Seasonally adjusted