Overview

Background

O.1 Published by the Office for National Statistics (ONS) since March 2024, the Price Index of Private Rents (PIPR) is a monthly series of official statistics in development that provides estimates of private sector rent levels and change for Great Britain (GB). ONS developed PIPR to overcome known limitations of its previous private rental sector statistics, which were unable to provide estimates of private rent levels and change that were both comparable over time and available at low levels of geography. These limitations were previously identified in the UK Statistics Authority (UKSA)’s Systemic Review on Housing and Planning Statistics in 2017. As a result, PIPR has now replaced ONS’s Index of Private Housing Rental Prices (IPHRP) and Private Rental Market Statistics (PRMS). An important use of the new PIPR estimates is for estimating the owner occupiers’ housing costs (OOH) element of the Consumer Prices Index including OOH (CPIH). 

O.2 ONS requested that we assess its PIPR statistics against the Code of Practice for Statistics with a view to them becoming accredited official statistics. Assessments support the development of new statistics by identifying and indicating to producers how they can enhance their overall value for users.  

O.3 This report represents the first phase in the assessment process. It concludes that: 

• There are five Requirements that ONS will need to address as it further develops the PIPR statistics. These requirements need to be met before we will consider initiating a full assessment of whether these statistics merit accredited official statistics status.
• ONS must publish an action plan setting out how it will address the five assessment Requirements, and report back to us publicly every three months on its progress. 

Judgement on Accredited Official Statistics Status

O.4 This assessment was carried out against the Code of Practice for Statistics. It also drew on the Office for Statistics Regulation (OSR)’s Spotlight on Quality Framework, which examines four key areas to evaluate the quality of statistics: whether the statistics are produced using suitable data sources; whether appropriate methods are used; whether transparent quality assurance is undertaken; and whether the statistics are sufficiently prioritised and resourced proportionately to their use. The framework also considers whether the statistics meet the quality needs of users and are not misleading. 

O.5 This assessment found that ONS’s new PIPR statistics generally appear to be meeting users’ needs more effectively than the previous private rents measures that these statistics have replaced. Users were also generally positive about ONS’s open approach to engagement during the development of PIPR, especially in Autumn 2023, ahead of the first publication of PIPR estimates in March 2024. 

O.6 Feedback from many of the users that we spoke to indicated that ONS’s engagement around PIPR’s development was open, positive and helpful. The range of resources that ONS has produced and its efforts to engage with a wide range of users ahead of PIPR’s initial publication were also extensive. This engagement approach may be a good model for ONS to use ahead of launching other future statistics developments. 

O.7 However, users have had only a few months to test the PIPR estimates, and the Northern Ireland (NI) and UK estimates are not due for publication until March 2025. Additionally, although ONS has published supporting methods and quality documentation for PIPR, this does not currently amount to a sufficiently accessible and detailed account of PIPR methods to enable an adequate understanding of the approaches used, ONS’s rationale for choosing them, and their relative strengths and limitations, for both technical and non-technical users. There is also a need for detailed metadata to enable a better understanding of the quality of the rents data used to produce monthly PIPR estimates, for which quality issues at low levels of geography are likely.  

O.8 Given the voluntary nature of data submission and the different types of private rents data drawn from across the UK, further work is needed to demonstrate that PIPR is produced using suitable data sources. ONS needs to enhance its published material on the quality of the source data and the quality assurance that is undertaken. ONS will need to develop and publish the necessary materials; publish NI and full UK PIPR-based estimates; and facilitate an effective evaluation of the UK PIPR series with users before we will consider initiating a full assessment of whether these statistics merit accredited official statistics status.  

Key Findings

O.9 Collecting private rents data consistently is challenging. The administrative rents data used to produce monthly PIPR estimates, and previously IPHRP, are collected individually by each UK nation for the primary purpose of setting annual Local Housing Allowance (LHA) rates, and they vary in their precise definition and quality. ONS has good relationships with its data suppliers, but it does not currently publish metadata on the quality and representativeness of the private rents data that PIPR estimates are based on each month, for which quality issues at low levels of geography are likely due to variations in the volume and spread of local rents data supplied over the year.  

O.10 Despite the inclusion of some specific caveats in the PIPR bulletin, differences in data definitions have also led to concerns about misleading comparisons being made at local levels or between GB nations. These concerns are particularly prevalent when making comparisons with rents estimates for Scotland, where the source data are primarily based on advertised rents, rather than actual agreed rents, as is the case in England and Wales. As with the IPHRP data currently, PIPR estimates for NI – to be published from March 2025 – are also planned be produced using advertised rents data. 

O.11 ONS developed the PIPR methods collaboratively with experts. These methods are similar to those used for the UK House Price Index. The users that we spoke to generally see PIPR as an improved series that better meets their needs. In particular, many noted that PIPR appears to be more responsive to inflationary changes than the previous IPHRP series.  

O.12 However, some users consider that the dissemination of the statistics does not meet their needs. In particular, the information published on the PIPR methods is too high level for some expert users who want to understand exactly how PIPR methods work in detail, while some non-expert users would prefer a clearer and more accessible methods summary with worked examples. Where users raised methodological concerns, these focused on conceptual issues about rental price calculations being based on the ‘stock’ of all available lets, rather than alternatives such as the ‘flow’ of newly re-advertised lets only.  

O.13 It will be important for ONS to publish sufficient information on PIPR methods and data quality to support adequate user understanding. This information will also be essential for ONS’s evaluation of PIPR’s ‘in development’ status with PIPR users. However, there are ongoing challenges with publishing more-detailed or visual information due to ONS’s publication word count and accessibility policies. ONS told us that it hoped to address these barriers in the medium term through planned changes to the ONS website.  

O.14 Many users told us that they welcomed ONS’s open and engaging approach during PIPR’s development ahead of the estimates’ initial publication in March 2024. These engagements included a series of effective public information sessions that ONS provided during PIPR’s development in Autumn 2023. However, beyond plans to publish NI and UK estimates from March 2025, users are unclear what further developments to PIPR statistics ONS might be planning over the coming months, including in response to additional user requests. ONS has yet to clearly communicate many of its development plans, or how it will engage with users and support their use of the new series now that it is in regular production. In particular, although users who employ PIPR for housing market analysis are now better served by more-detailed local estimates, it is unclear how ONS plans to further support this use.  

O.15 ONS’s Stakeholder and Technical panels on consumer prices provide good opportunities for user challenge to ONS’s approaches to measuring inflation, including in the development of PIPR, with most previous panel papers and minutes being transparently published. However, many papers relating to PIPR’s development were not published due to their market sensitivity at the time. It would be helpful for ONS to review whether these historical papers remain market sensitive and whether, with the consent of the data owners, they can be published to further support transparency and user understanding of the PIPR development process. 

Next Steps

O.16 Given the issues and concerns outlined above, we have identified five requirements that ONS must address as it develops the PIPR estimates in order for its statistics to meet the standards required by the Code of Practice for Statistics and before they could be considered for a full assessment as to whether they merit accredited official statistics status (called National Statistics in the Statistics and Registration Service Act 2007): 

Requirement 1: In the context of the purposive sampling approach used; variations in the types, volume and spread of local rents data supplied over the year across the UK nations; and the potential for bulk data submissions and lags in recording rental price changes, ONS should:  

• publish a detailed account of the quality and representativeness of the private rents data that PIPR estimates are based on each month, in relation to the types of data collected where possible (agreed vs advertised) by property type and geography 
• publish additional information on its approach to assessing the quality and representativeness of the private rents data each month, including the extent to which the rents data submitted meet expected monthly volumes 

Publishing this information should provide insight to users about the quality of PIPR source data and enable a more meaningful understanding of variations in rent data quality and the approaches that ONS statisticians take to identify and highlight data quality issues, which are particularly likely to impact PIPR estimates at low levels of geography.  

Requirement 2: Given the complexity of the methods chosen and variations in source data quality across the nations and over the year, ONS should publish more-detailed and accessible information on PIPR methods and quality to allow a complete understanding of the approaches taken and support their appropriate interpretation for a range of users and uses. In publishing this, ONS should: 

• improve its communication of the quality of and uncertainty in the PIPR estimates, by including sufficiently detailed information for expert users; having shorter accessible explanations with worked examples for non-expert users; and ensuring greater consistency in the communication of key methods and quality information across the different PIPR products 

• be clear about how the PIPR methodology works for the different source data used, including, for example, rents source data being predominantly on an advertised basis in Scotland, and completely on an advertised basis in NI. ONS should be clear about why the same method is used even though the data sources differ 

• set out in more detail aspects of the methods choices made, including, for example, how the PIPR weights are calculated; the rationale for the data sources chosen to weight PIPR estimates; the chain-linking methods used to combine the PIPR and historical IPHRP series; and the relative strengths and limitations of these methods 

• provide a clearer rationale for choices made, for example, combining PIPR and IPHRP estimates in the presented UK totals, and clear guidance on the extent of comparability of estimates for the different UK nations 

• provide a fuller explanation of its approach to revising provisional UK PIPR estimates owing to NI data only becoming available two months after GB data. This should support a more transparent user understanding of the nature and extent of revisions made to PIPR estimates and make it clear that these are the only revisions made 

Requirement 3: ONS should publish information on its strategy for engaging with a range of PIPR users beyond PIPR’s initial publication, including once the UK index is published, and particularly how it will support users of PIPR for housing market analysis. Publishing this will help users see how their needs will be understood and supported and maximise the value of further PIPR developments. ONS should publish a summary of the user feedback that it receives from its evaluation of PIPR’s ‘in development’ status once the full UK PIPR index is published.  

Requirement 4: To support user understanding of ONS’s development approach, ONS should clearly communicate any further planned improvements that it intends to make in response to user feedback, and which user requests it will and will not take forwards. ONS should also publish its plans for evaluating PIPR’s ‘in development’ status once it has published NI and UK estimates and for taking forward findings from its own reviews of PIPR data quality and methods. Doing so will support users’ confidence in ONS’s approach to developing UK PIPR estimates; ensure that users are aware of planned and potential future improvements; and maximise the quality and value of future developments. 

Requirement 5: To support transparency and user confidence in the governance and oversight of consumer prices, ONS should review which of its historical panel minutes and papers that relate to PIPR’s development and were restricted due to market sensitivity may now be suitable for publication, subject to the consent of the data owners. 

O.17 ONS must publish an action plan by January 2025 setting out how it intends to address these five requirements, and report back to us publicly every three months on its progress.