Number of houses included in the HPI for the last 2 years

Dyddiad y datganiad:
2 November 2021

FOI Ref: FOI/2021/3152

You asked

Please advise how many houses were included in the HPI more than once and how many were left out per month for 2 years?

We said

Thank you for your request.

The requested information regarding the number of houses that were included in the HPI more than once per month for 2 years can be calculated from our publicly available datasets, accessible via the following link: https://www.gov.uk/government/statistical-data-sets/uk-house-price-index-data-downloads-august-2021 (please update the month and year within the link to the month’s publication that you are interested in).

For the most recent published data (published on the 20th October 2021), the following pooling was applied:

  • January 2021 includes all new build transactions from December 2020 and January 2021 for England and Wales. This meant all 4,515 new builds from December 2020 in England and Wales were used in the calculation of January 2021

  • February 2021 includes all new build transactions from January and February 2021 for England and Wales. This meant all 1,590 new builds from January 2021 in England and Wales were used in the calculation of February 2021

  • March 2021 includes all new build transactions from February and March 2021 for England and Wales. This meant all 1,519 new build transactions from February 2021 in England and Wales were used in the calculation of March 2021

  • April 2021 includes all new build transactions from March and April 2021 for England and Wales. This meant all 1,509 new build transactions from March 2021 in England and Wales were used in the calculation of April 2021

  • May 2021 includes all new build transactions from April and May 2021. This meant all 585 new build transactions from April 2021 in England and Wales were used in the calculation of May 2021

  • June 2021 includes all new build transactions from May and June 2021. This meant all 355 new build transactions from May 2021 in England and Wales were used in the calculation of June 2021

  • July 2021 includes all new build transactions from June and July 2021. This meant all 480 new build transactions from June 2021 in England and Wales were used in the calculation of July 2021

  • because of the nature of the processing of the new builds, these are never included in the model for the first estimate, so August 2021 has not been affected

If you would like to understand previous iterations of the UK House Price Index you are able to extract this data yourself from published information. In order to calculate this information please:

  1. Download the publicly available datasets (UK HPI full file) published on GOV.UK for the month of publication that you would like to investigate.
  2. Filter to England and Wales (these are the only countries affected by pooling)
  3. Scroll across to "NewSalesVolume". This reports the number of new build transactions for each month.
  4. Open the ONS House Price Index bulletin for the month of publication that you would like to investigate, and navigate to Measuring the Data > Coronavirus. This explains what pooling has been applied for each month.
  5. To calculate how many new build properties have been used you can use the ONS House Price Index bulletin to understand which months have been used to pool, and use the "NewSalesVolume" to understand how many transactions were used in that pooling process.

Should you have any issues with calculating this information yourself, or would like this task to be conducted by a member of our team, we are able to offer this service for a charge in line with our charging policy. We estimate that this task would take 3 to 5 days to complete. Bespoke services are subject to legal frameworks, disclosure controls, resources and agreement of costs. If you would like to discuss the provision of this service, please contact hpi@ons.gov.uk to discuss your enquiry further.

As the information prior to 2021 can be calculated from publicly available datasets, and the information can also be provided via our bespoke services for a charge, Section 21 of the Freedom of Information Act 2000 (FOIA) applies. This exemption applies when information is reasonably accessible via another route.

Regarding your request for the number of houses that were left out of the of the HPI per month for two years, we can confirm that this figure is 0. We use all available data at the point of extraction to calculate the HPI. Sales in the most recent months may not reflect the actual number of sales because of the time it can take for a sold property to be registered with HM Land Registry. Transactions for previous months will continue to feed through into the UK HPI dataset for a period after they were initially sold (12 months, in line with our revisions policy).

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