Estimating the number of rooms in Census 2021: an update on deriving an occupancy rating from Valuation Office Agency number of rooms

• The Office for National Statistics (ONS) intends to reduce respondent burden by linking Valuation Office Agency (VOA) information on number of rooms to Census 2021; previous research demonstrated the feasibility of using VOA number of rooms and that donor-based imputation can predict missing VOA number of rooms; we also published our quality assurance of VOA data used in Census 2021.
• Because of the definitional differences between the census and VOA number of rooms measures, the VOA occupancy rating is typically 1 less than the census occupancy rating at household level (median difference is negative 1 for all local authorities and the mean difference varied between negative 1.7 and negative 0.6); our analysis has adjusted for this difference when making comparisons.
• Our analyses indicated that the (adjusted) proportion of overcrowded households is likely to be smaller when using the VOA room occupancy rating compared with the 2011 Census room occupancy rating.
• VOA room occupancy rating produces national levels of overcrowding for private rental and social rental households that are similar to each other, compared to using census room occupancy rating where they differ.
• There are most likely two drivers for these differences: firstly, VOA does not count kitchens, conservatories and utility rooms, secondly, the means and purposes of data collection for census and VOA are different; these effects will vary across tenure and accommodation type.
• Additional care has to be taken when looking at sub-regional comparisons as the level of overcrowding is not consistently lower across the whole of England and Wales; we strongly encourage users to familiarise themselves with the full analysis presented in Section 4.
• At least two-thirds of local authorities would be ranked in the same order based on the level of overcrowding independent of which of the two measures is used.
• To adjust for this definitional difference for the 2021 Census, we recommend that the VOA room occupancy rating calculation is adjusted by adding one room. This new variable should be referred to as “occupancy rating (VOA number of rooms)”.

Disclaimer

This research does not provide official statistics on housing nor is it used in the underlying methods or assumptions in the production of official statistics. Rather, it is published to allow users to understand a new methodology that is different to that used in the 2011 Census to measure the number of rooms in households. These outputs should not be used for policymaking or decision-making.

It is important that the information and research presented are read alongside the analysis to aid interpretation and avoid misunderstanding. These analyses must not be reproduced without this disclaimer and warning note.

Replacing the number of rooms question in Census 2021

The Census 2021 topic consultation recommended to continue collecting information on the number of bedrooms from the census, as this is used to derive measures of overcrowding and under-occupancy. Number of rooms on the census primarily meets the same information needed as number of bedrooms. The Office for National Statistics (ONS) intends to reduce respondent burden by using alternative sources to provide information on number of rooms as announced in the Census 2021 White Paper, Help Shape Our Future: The 2021 Census of Population and Housing in England and Wales (PDF, 967KB).

Our previous assessment of the feasibility of using Valuation Office Agency (VOA) data to replace the number of rooms question concluded that the direct agreement rate between the 2011 Census and VOA data for number of rooms was 16%. This was primarily attributable to definitional differences between the 2011 Census and VOA rooms variables. Census estimates of the number of rooms include kitchens, utility rooms and conservatories, which VOA estimates do not. Since most properties have a kitchen, the number of rooms in the census data was generally higher than the corresponding number of rooms in the VOA data. If we assume that the number of rooms derived using VOA data records is at least one room less than when derived using the census data, the agreement rate increases to 48%.

Comparatively, the quality of the census responses for number of rooms was measured by the 2011 Census Quality Survey (CQS) (PDF, 1.4MB) at 67%. The survey found that differences occurred because respondents had misunderstood the question. Most of these differences (93%) were within plus or minus one room.

Using VOA number of rooms for Census 2021 does imply a discontinuity with 2011 Census estimates (because of the definitional difference) that users need to be aware of. It will not be appropriate to measure change in number of rooms from 2011 to 2021; instead, the census bedroom question can be used for comparisons over time. Using the number of rooms in the VOA data for Census 2021 will provide a high-quality relative measure of size, enabling the comparison of households between areas within the same time period, whilst reducing respondent burden.

Incorporating VOA data into the census requires linking the two data sources together. Our method for linking the two data sources is described in Section 4. An imputation process is required to ensure that the quality of Census 2021 outputs is not impacted by households that are missing number of rooms because of either a failure to link to VOA data or missing values in VOA data. A summary and methodology article explaining our approach for addressing missingness in the linked census and VOA data have been published.

This is the first time we are using administrative data linked to the census to produce a new type of statistical output. This article explores how this methodological change will impact derived variable outputs. Specifically, we are comparing the occupancy rating derived from the 2011 Census number of rooms question and linked VOA number of rooms data. We want to provide further assurance in preparation for the replacement of the number of rooms question in Census 2021. This article will prepare our users for the differences between the two methodologies and help with understanding the reasons behind them.

We have also published our research into using VOA number of bedrooms to estimate levels of overcrowding and if it could be used to supplement household surveys to calculate the bedroom standard.  

Measuring overcrowding using room occupancy rating

Housing policy is concerned with the availability and quality of housing. An important aspect when assessing living conditions is the amount of living space available to a household. Accommodation that does not provide enough space for a household of a given size is considered “crammed” or overcrowded (PDF, 681KB).

Overcrowding is often measured using an occupancy rating. An occupancy rating is obtained by subtracting a hypothetical number of rooms (or bedrooms) recommended for a household from the actual number of rooms (or bedrooms) it has available. A household is considered overcrowded if it has fewer rooms (or bedrooms) available than recommended (negative occupancy rating), or under-occupied if it has more (positive occupancy rating). This makes the occupancy rating a straightforward way of measuring overcrowding and under-occupancy.

In England and Wales, three different standards are commonly used to assess whether the living space available to a household is overcrowded. The Housing Act 1985 defines two of these standards: the room standard and the space standard. The Act states that if a household does not meet these standards it should be classed as overcrowded. However, in 2012 the Department for Communities and Local Government (DCLG, now MHCLG) issued guidance, Allocation of accommodation: Guidance for local housing authorities in England, which recommended that local authorities should use the non-statutory bedroom standard when assessing whether or not households are overcrowded for the purpose of housing allocation.

The room standard is the only one of these three that uses the number of rooms available to a household. The Housing Act 1985 ignores children under the age of 10 when determining the hypothetically required number of rooms and considers all bedrooms and living rooms to be able to provide sleeping accommodation.

In contrast, the 2011 Census uses a slightly more sophisticated occupancy rating based on number of rooms. A lone person household is assumed to require three rooms: one bedroom and two common rooms (for example, kitchen, dining or living room). All other households require two common rooms plus one additional bedroom for each:

• adult couple
• any remaining adult (aged 16 years or over)
• two adolescents (aged 10 to 15 years) of the same sex
• one adolescent (aged 10 to 15 years) and one child (aged 9 years or under) of the same sex
• two children (aged 9 years or under) regardless of sex
• any remaining child (aged 9 years or under)

This definition is the most widely used occupancy rating for number of rooms, despite being non-statutory (that is, not written into law). For the rest of this article we will refer to this definition when we use “room occupancy rating”.

Measuring household housing deprivation and the Index of Multiple Deprivation

The 2011 Census measured household housing deprivation (HHD). A household was considered deprived, if it was overcrowded (using the room occupancy rating in England and the bedroom standard in Wales), was a shared dwelling, or had no central heating.

Furthermore, central government, local authorities and health services assess levels of deprivation using the Index of Multiple Deprivation (IMD) and Carstairs index. The IMD is the most common measure of deprivation and is produced by each country in the UK.

The English Indices of Deprivation (English IMD) and the Welsh Index of Multiple Deprivation (Welsh IMD) rank Lower layer Super Output Areas (LSOA) based on the level of deprivation relative to each other within each of the following domains: income, employment, education, health, crime (or community safety), living (or physical) environment, housing and access to services.

Households may be counted as being deprived in one or more of these domains, depending on the number of types of deprivation that they experience. This information is then brought together into an overall index of multiple deprivation. Overcrowding is assessed as part of the housing domain of the IMD. The English IMD uses the room occupancy rating to calculate overcrowding, whereas the Welsh IMD uses the bedroom standard.

One purpose of this research was to assess the difference to HHD and IMD that could occur from replacing the census number of rooms question with Valuation Office Agency (VOA) number of rooms data.

Using 2011 Census to derive an occupancy rating for VOA number of rooms

We linked 2011 Census data to Valuation Office Agency (VOA) data to assess the difference between deriving occupancy ratings from the census number of rooms question and from VOA number of rooms.

The 2011 Census data were linked to 2016 VOA data at address level using unique property reference numbers (UPRNs). Properties in the VOA data that were built after 2011 were removed prior to linkage to enable better comparison with the census data. The 2011 Census records that could not be assigned a UPRN were also removed.

We used the “raw” 2011 Census data to compare 2011 Census number of rooms question with VOA number of rooms. This means that the numbers presented here are not adjusted for household and within household non-response and will differ from previously published estimates (as shown in Section 5).

This is the same methodology used in previous research and a more detailed description of the linkage methodology can be found in the previous publication, ONS working paper series number 20 (Section 13).

Statistical differences between 2011 Census number of rooms question and VOA number of rooms

We have previously explored the relationships between the 2011 Census number of rooms question, as well as VOA number of rooms to the 2011 Census household variables¹ using several linear regressions. 2011 Census household variables were used as predictors and the two number of rooms variables were outcome variables. Comparing the regression coefficients showed that the relationship between the 2011 Census household variables and the 2011 Census number of rooms variable appeared similar to the relationship with the VOA number of rooms variable across all of the 2011 Census household variables.

This finding allows us to infer that the 2011 Census and VOA number of rooms variables are measuring similar statistical concepts. The number of rooms predicted using the VOA number of rooms variable was approximately 1 room less than the number of rooms in the 2011 Census. This is consistent with the definitional differences between the two sources².

We expanded on this research by exploring the relationship between 2011 Census household variables and the difference between census number of rooms and VOA number of rooms. The 2011 Census household variables were used as predictors and the outcome variable was calculated by subtracting the VOA number of rooms from census number of rooms for each household. Categorical household variables were dummy coded.

If census number of rooms and VOA number of rooms are truly statistically similar, then we would expect the difference between the two number of rooms variables to be random and therefore unrelated to the predictor variables, that is, the unstandardised beta coefficients should be close to zero (that is, the unstandardised beta coefficients should be close to zero).

Table 1 shows the results of regression analyses predicting the difference between 2011 Census number of rooms and VOA number of rooms from 2011 Census accommodation type (compared with the base category). The intercept was close to 1, which would be expected because of the definitional difference² between census number of rooms and VOA number of rooms.

Detached houses had a relatively large unstandardised beta coefficient of 0.70. This means that for detached houses the mean number of rooms estimated by census is 0.70 more than the mean number of rooms estimated by VOA. It is quite likely that this occurred because detached houses are more likely to have conservatories and utility rooms, which are counted by census but not the VOA. To a lesser extent that is also true for semi-detached houses (unstandardised beta coefficient of 0.23). For a block of flats we can observe the opposite effect (unstandardised beta coefficient of negative 0.16), which might indicate that flats are less likely to have a kitchen as a separate room.

Table 2 shows the results of regression analyses predicting the difference between 2011 Census number of rooms and VOA number of rooms from 2011 Census tenure (compared to the base category). Again, the intercept was close to 1. For owner-occupied households the mean number of rooms estimated by the census is larger than the mean number of rooms estimated by VOA (unstandardised beta coefficient of 0.33 and 0.39). There is likely a relationship between tenure and accommodation type, which we will explore in more detail in Section 5.

The regression results for other 2011 Census household variables can be found in Section 8.

While there are similarities between the census and VOA number of rooms measures there are also clear differences, which are partially explained by the census household variables. Users will need to be aware of these differences, which are most notable for detached houses and owner-occupied properties.

Therefore, it will not be appropriate to measure change in number of rooms from 2011 to 2021; instead, the census bedroom question can be used for comparisons over time. For Census 2021, VOA number of rooms will provide a high-quality relative measure of size enabling the comparison of households across areas within the same time period.

Occupancy ratings for 2011 Census number of rooms and VOA number of rooms

There are several reasons why we would expect the occupancy ratings for 2011 Census number of rooms and VOA number of rooms to measure a similar statistical concept. Firstly, both census and VOA room occupancy ratings are calculated using the number of rooms hypothetically required by a household. In both cases, the number of rooms required is derived from the census questionnaire response using the number of household members and their relationships to each other (see Section 3). Secondly, we found that census number of rooms and VOA number of rooms measure similar statistical concepts.

Finally, the room occupancy rating is simply the difference between hypothetical number of rooms required and the actual number of rooms available. Therefore, we expect the census room occupancy rating and VOA room occupancy rating to measure a similar statistical concept and expect the VOA room occupancy rating to be typically 1 less than the census room occupancy rating.

Our further analysis has demonstrated that this is indeed the case. We found the median difference between the VOA occupancy rating and the 2011 Census occupancy rating was negative 1 for all local authorities, while the mean varied between negative 1.7 and negative 0.6.

Notes for: Deriving an occupancy rating for VOA number of rooms

1. The census household variables are:

   • number of usual residents
   • accommodation type
   • landlord
   • tenure
   • number of bedrooms
   • central heating
   • number of cars or vans

2. Census counts kitchens, which VOA does not. See Section 2 for more detail.

Levels of overcrowding for 2011 Census number of rooms and VOA number of rooms

The room occupancy rating is used to identify the proportion of overcrowded households. Households are considered overcrowded if the census room occupancy rating is “negative 1 or less” (see Section 3).

Because of the definitional differences between the census and Valuation Office Agency (VOA) number of room measures, the VOA occupancy rating is typically 1 less than the census occupancy rating (see Section 4). Therefore, we expect the proportion of overcrowded households calculated using the census room occupancy rating of “negative 1 or less” to be comparable with the proportions calculated using a VOA room occupancy rating of “negative 2 or less”. These thresholds are used for the rest of this article even when not explicitly stated.

Changes in the reported level of overcrowding over time are likely to draw public attention and may affect policy decisions. Our aim is to highlight that these changes will be driven by a change to the way we measure overcrowding using VOA number of rooms in Census 2021 and users will not be able to make direct comparisons with 2011 Census.

It is well documented that levels of overcrowding vary with tenure type (PDF, 681KB). The level of overcrowding for private rental sector (PRS), social rental sector (SRS) and owner-occupied households is shown in Figure 1 for England and in Figure 2 for Wales.

It is worth noting that the “raw” 2011 Census data used in this article have not been adjusted for household and within household non-response (see Section 4), which explains the lower level of overcrowding for PRS and SRS compared with official 2011 Census estimates.

For PRS and SRS, the level of overcrowding is lower for VOA room occupancy rating (with a threshold of “negative 2 or less”) than for the census room occupancy rating. Importantly, the census room occupancy rating records a higher level of overcrowding for PRS in comparison with SRS. This difference cannot be observed for the VOA room occupancy rating (with a threshold of “negative 2 or less”). There are no notable differences in the level of overcrowding for owner-occupied households, which is generally low.

There are most likely two drivers for these differences. Firstly, VOA does not count kitchens, conservatories and utility rooms (see Section 2). For our comparison, we partially adjusted for this difference by applying a lower threshold to the VOA room occupancy rating when flagging households as overcrowded. However, this naïvely assumes that this difference is the same for all tenure and accommodation types (for example, all properties have a kitchen). But, flats are more likely to be lacking a separate kitchen (for example, studio flats) and there is likely a difference in the prevalence of flats without a separate kitchen between SRS and PRS.

Secondly, the means and purposes of data collection for census and VOA are different. VOA make every effort to collect accurate and up-to-date data and maintain their accuracy, but data updates are primarily linked to the sale of properties and is primarily concerned with establishing the “value” of a property. As part of our quality assurance of VOA data used in Census 2021 we noted that there is the potential for distortive effects, which will vary by geography and type of property.

Comparing levels of overcrowding at local authority level for 2011 Census number of rooms and VOA number of rooms

In Section 4, we noted differences between census number of rooms and VOA number of rooms for different accommodation types. And in Section 5, we confirmed that levels of overcrowding vary with tenure type, but these patterns are not fully preserved when replacing the census number of rooms question with VOA number of rooms.

We want to provide users with some insight into the sub-regional differences by tenure and accommodation type to help them understand this new measure of overcrowding. We have calculated the proportion of overcrowded households within each local authority using the census room occupancy rating of “negative 1 or less” and compared it with the proportions calculated using a VOA room occupancy rating of “negative 2 or less”, because the VOA occupancy rating is typically 1 less than the census occupancy rating (see previously). We used linear regressions to explore the relationship between these two measures as recorded in Table 3.

We found that a large proportion of the variation for the census room occupancy rating also explains the variation of the VOA room occupancy rating (as the R² are large). However, for semi-detached houses in the social rented sector the proportion of variation that can be explained is relatively small.

Reassuringly, the intercepts for all comparison are very close to zero, which means that both measures accurately estimate small levels of overcrowding. However, the gradients are consistently less than 1. A smaller proportion of households will be flagged as overcrowded using the VOA room occupancy rating (with a threshold of “negative 2 or less”) compared with using the census room occupancy rating. The proportion will be most similar for owner-occupied terraced houses and the least similar for owner-occupied flats.

There are most likely two drivers for these differences. Firstly, different types of housing will be predominant for certain combinations of tenure and accommodation type. Secondly, adjusting for definitional differences between VOA number of rooms and census number of rooms by applying a lower threshold to the VOA room occupancy rating when flagging households will not have a uniform affect for different accommodation types.

For example, houses more commonly have conservatories and utility rooms, which are recorded by the census question but not the VOA. But, flats are more likely to be lacking a separate kitchen (for example, studio flats) and there is likely a difference in the prevalence of flats without a separate kitchen between SRS and PRS.

Differences of levels of overcrowding at local authority level for 2011 Census number of rooms and VOA number of rooms

Figure 3 shows the percentage points difference between the proportion of overcrowded households calculated using the 2011 Census room occupancy rating and the proportion of overcrowded households using VOA room occupancy rating (with a threshold of “negative 2 or less”). The difference between these two measures has been calculated at the local authority level by tenure and accommodation type. A value of zero indicates that there is no difference in the 2011 Census and VOA estimates, positive values indicate that the proportion of overcrowded households is larger for VOA room occupancy rating compared with the 2011 Census room occupancy rating, and negative values indicate that the VOA proportion is smaller.

Figure 3 Percentage point (pp) differences in the levels of overcrowding at LA level for 2011 Census number of rooms and for VOA number of rooms using the respective room occupancy rating by tenure and accommodation type, England and Wales

Households are identified as overcrowded if they have a room occupancy rating of “-1 or less” using 2011 Census number of rooms or “-2 or less” for VOA number of rooms.

Notes:

1. This work uses research datasets, which may not exactly reproduce National Statistics aggregates.
2. Proportions of overcrowding have been suppressed if an LA had fewer than 10 overcrowded households or fewer than 100 households in total for a given tenure and accommodation type.
3. A value of zero indicates that there is no difference in the 2011 Census and VOA estimates, positive values indicate that the proportion of overcrowded households is larger VOA room occupancy rating compared with the 2011 Census room occupancy rating, and negative values indicate that the VOA proportion is smaller.

Download the data

Our analyses in the previous subsection (see Table 3) indicated that the proportion of overcrowded households is likely to be smaller when using the VOA room occupancy rating (with a threshold of “negative 2 or less” to adjust for definitional differences) compared with the 2011 Census room occupancy rating.

This effect can be observed across England and Wales for flats of all tenure types. As discussed before, adjusting the VOA room occupancy threshold to “negative 2 or less” possibly overcompensates for flats that are more likely to be lacking a separate kitchen (for example, studio flats) and therefore the census number of rooms and VOA number of rooms are more likely to be identical for flats.

For the other accommodation types we want to draw users to the most notable differences. Contrary to the general trend, the proportion of overcrowded households is likely to be larger when using the VOA room occupancy rating (with a threshold of “negative 2 or less” to adjust for definitional differences) compared with the 2011 Census room occupancy rating:

• for owner-occupied properties outside of London, especially for terraced houses in the North West
• for private rental properties outside of London in some of the more urban local authorities (for example, Leeds, Canterbury, Bath) and especially for terraced houses in the North West
• for social rental properties outside of London there are various local authorities (for example, West Oxfordshire)

We also want to remind users that VOA make every effort to collect accurate and up-to-date data and maintain their accuracy, but data updates are primarily linked to the sale of properties. As part of our quality assurance of VOA data used in Census 2021 we noted that there is the potential for distortive effects, which will vary by geography and type of property.  

For 2011 Census, the room occupancy rating was one of three measures used to determine household housing deprivation (HHD). The room occupancy rating also contributes towards the housing dimension in the English Index of Deprivation (English IMD). See Section 3 for an introduction to both measures.

Valuation Office Agency (VOA) number of rooms is a suitable alternative to the census number of rooms question and can be used to generate a room occupancy rating for each address in Census 2021. Because of the definitional differences between the census and VOA number of rooms measures, the VOA room occupancy rating is typically 1 less than the census room occupancy rating (see Section 4). For 2011 Census, we considered households as overcrowded if they have a VOA room occupancy rating of “negative 2 or less” or a census room occupancy rating of “negative 1 or less”. See Section 5 for a complete discussion.

For the 2021 Census, we recommend that the VOA room occupancy rating is calculated by subtracting a hypothetical number of rooms recommended for a household (or “rooms required”) from the actual number of rooms it has available and adding 1, so that households are considered as overcrowded if they have a VOA room occupancy rating of “negative 1 or less”.

Even with this adjustment, the level of overcrowding calculated using the VOA room occupancy rating will not be directly comparable with the level of overcrowding calculated using the 2011 Census number of rooms question. Nationally, and for most local authorities, the VOA room occupancy rating tends to estimate a lower level of overcrowding in comparison with the census measure.

This will result in some addresses not being marked as deprived as part of the HHD (unless they are also lacking central heating or are a shared dwelling) or within the English IMD’s housing domain. However, the occupancy rating is one of multiple measures feeding into these two deprivation measures, which minimises the risk that these changes will affect the overall measure.

Furthermore, the English IMD combines multiple measures to rank Lower layer Super Output Areas (LSOA) by their level of deprivation. However, we were only looking at one aspect of a deprivation (that is, overcrowding) and because of small counts are not able to look at LSOAs.

We used Spearman’s rank correlation to assess if local authorities in England and Wales rank the same when calculating the level of overcrowding using the 2011 Census room occupancy rating and comparing it with the VOA room occupancy rating. Table 4 lists the Spearman’s rank correlation coefficient by tenure and accommodation type.

We found that the Spearman’s rank correlation coefficient is 0.64 or larger for all tenure and accommodation types. This means at least two-thirds of local authorities would be ranked in the same order based on the level of overcrowding independent of the measure used.

The number of rooms question will not be asked in Census 2021. Instead we will be using Valuation Office Agency (VOA) number of rooms to produce statistical outputs for number of rooms in Census 2021. This implies a discontinuity with 2011 Census estimates (because of the definitional difference) that users need to be aware of. To ensure users understand that this is a new measure, the Office for National Statistics (ONS) will be referring to “VOA number of rooms” (instead of just “number of rooms”) wherever possible.

It will not be appropriate to measure change in number of rooms from 2011 to 2021; instead, the census bedroom question can be used for comparisons over time. Using the number of rooms in the VOA data for Census 2021 will provide a high-quality relative measure of size, enabling the comparison of households between areas within the same time period.

As for 2011 Census, the ONS is planning on producing the room occupancy rating for Census 2021 and the household housing deprivation measure. Because of the definitional difference between 2011 Census number of rooms question and VOA number of rooms, there will be a discontinuity with 2011 Census estimates for these measures. We strongly encourage users to read through the analysis presented here to understand these differences.

On average, the (unadjusted) room occupancy rating derived from VOA number of rooms will be 1 less than the occupancy rating derived from census number of rooms (see Section 4). To adjust for this definitional difference, we recommend that the VOA room occupancy rating for Census 2021 is calculated by subtracting a hypothetical number of rooms recommended for a household (or “rooms required”) from the actual number of rooms it has available and adding 1, so that households are considered as overcrowded if they have a VOA room occupancy rating of “negative 1 or less”. This new variable should be referred to as “occupancy rating (VOA number of rooms)”.

Despite this adjustment, we expect the national level of overcrowding using the VOA room occupancy rating to be lower than what would be expected if we continued to use the number of rooms question in Census 2021. Additional care has to be taken when looking at sub-regional comparisons as the level of overcrowding is not consistently lower across the whole of England and Wales. We strongly encourage users to familiarise themselves with the full analysis presented previously and especially some of the differences observed by tenure and accommodation type.

Finally, we would like to note that the 2011 Census number of rooms question included kitchens, conservatories and utility rooms. These are not counted by the VOA and these types of rooms are not generally considered as “habitable” rooms (such as bedrooms and living rooms). Therefore in the future VOA room occupancy rating could provide a more accurate way of determining if a household should be considered overcrowded and can be used alongside other measurers of overcrowding to better understand people’s living conditions in England and Wales.  

In this section we present supplementary results for linear regression results predicting the difference between 2011 Census number of rooms and Valuation Office Agency (VOA) number of rooms from 2011 Census household variables that were not reproduced in Section 4. The tables for the linear regression results predicting the difference between 2011 Census number of rooms and VOA number of rooms from 2011 Census accommodation type and tenure can be found in Table 1 and Table 2 respectively in Section 4.

Transforming population, migration and social statistics

We are transforming the way we produce population, migration and social statistics to better meet the needs of our users and to produce the best statistics from all available data. This includes the use of Valuation Office Agency (VOA) property attribute data to provide information on the number of rooms instead of asking a question on the Census 2021 questionnaire.

More information about the programme of work to put administrative (admin) data at the core of population, migration and social statistics is available. More information about the VOA data can be found in the source overview, and a summary of the quality assurance we have undertaken on it for Census 2021 is available.

Feedback

We welcome users providing feedback on this research and the methodology used to produce them, including how they might be improved and potential uses of the data. Please email your feedback to admin.based.characteristics@ons.gov.uk and include “Housing” in the subject line of your response.

Contact details for this methodology change

Joe Herson, Emily Mason-Apps, Stephan Tietz
Email: admin.based.characteristics@ons.gov.uk