We’ve been seeing a greater interest in our own House Price Index (HPI) each month, so we thought it could be a good time to provide some more information about what we publish each month and how we calculate it. Our HPI captures changes in the value of residential properties. Based on our price paid data it uses data collected on residential transactions, whether for cash or with a mortgage dating back to January 1995. It includes figures at national, regional, county and London borough level and is the only index based on repeat sales for England and Wales.
So what do we mean by repeat sales?
The HPI is a repeat sales regression (RSR) index, measuring average price changes in repeat sales on the same properties, ensuring a like for like comparison between properties. This means that price changes of a flat in Mayfair are not compared to those of a flat in Old Kent Road. The price paid data is currently made up of over 19 million transactions of which over 7 million are identifiable matched pairs, a number which increases with each publication.
Why do we use RSR?
The RSR approach is shown to be the best method of constructing an HPI using our data, as it is the most information efficient, as well as the most accurate. An alternative, the hedonic regression has been shown to be as good as the RSR method, but unfortunately it requires property characteristic data such as number of bedrooms or square footage, something that is not available in the HM Land Registry dataset.
What data do we publish?
As part of our commitment to the Governments Open Data initiative we not only publish our most recent HPI in PDF format, we also release all background data tables in a variety of formats for different accessibility needs:
- Official monthly HPI publication – the most recent publication which also includes an alternate index which takes into account repossession sales (pages 14 and 15)
- Background data tables – recalculated and issued each month, these tables contain the data that goes into creating our HPI each month, including non-seasonally adjusted data, it can be accessed via excel and csv files or as linked data
- Search facility – find average price, sales volumes and property type for a specified location over a defined period of time
Our HPI is recognised as an official statistic and in accordance with the code of practice is released each month on the 20th working day at 9:30am. Our HPI Calendar provides notice of our publications 12 months in advance. For more information on our HPI and the methodology applied, please see our FAQs and HPI Methodology. For information about work with the four official producers of house price statistics, which includes working towards a single definitive UK HPI, please see our latest house price notification. This collaborative approach would hopefully allow the publishing of consistent HPI data at a national, regional and sub-regional level across the UK. Please look out for more information on this in future blogs from us.