The Residential Mobility Index provides an estimate of the "churn" of the residential population in the UK - the proportion of households that have changed between the beginning of 2023 and the end of each of each year going back to 1997.

The estimates were built by linking administrative and consumer data, including electoral registers, consumer registers and land registry house sale data. These data enable research to explore annual variations in neighbourhood change at a small area geography. Crucially it also enables research to focus on yearly data rather than relying on decadal census data to estimate change. It is even possible to observe trends that have occurred since the collection of the 2011 or 2021 Census of Population.

The data present a ratio of the households that are different in each Local Authority District (LAD) or Lower Layer Super Output Area (LSOA) between the beginning of 2023 and the end of each year going back to 1997.

Residential mobility ("Population Churn") is estimated at the household level. Households’ start and end dates are extracted from individual level data by combining individuals that at any point in time have shared time together in the same property or have a shared surname in the same property. First household member determines the ‘start’ date (household identified as moving in), last household member determines the ‘end’ date (household identified as moving out).

These data are available at LAD (2021 boundaries) and LSOA (2011) boundaries. They can be downloaded from the bottom of the page. For detailed description of the columns contained within the data, see the Variable Dictionary; and for an overview of the characteristics of the data, see the Data Summary. These files can be downloaded from the bottom of this page.

Quality, Representation and Bias
As the data is inputted from several different organisations, it is possible that some names and addresses are inconsistently formatted between datasets. This would have hampered data linkage when making the index. For instance, we estimate that 100,000 surnames are misspelled/recorded slightly differently in each register.

In addition, addresses (particularly flats) can be recorded differently. Addresses are recorded as address lines. This makes address matching to other data quite difficult as the number and composition of address lines varies by addresses, and between different versions of the data too.

Lastly, it is very difficult to determine the completeness of the data. It is possible that deceased adults are not removed immediately and often not until new individuals are registered at their address. This means that RMI values in the last few years (2018-23) should be interpreted with caution given the delay in the change of registered addresses for individuals. Generally, town centres are underrepresented though. The earlier consumer registers (2003-12) and later electoral registers (2018-20) tended to under represent the adult population relative to mid-year population estimates. However, efforts were made by the CDRC to fill in any gaps where possible. The data for Northern Ireland is also estimated to be less complete due to distinctive administrative procedures in the region. It is also possible that adults who reside in multiple addresses may have duplicate entries within the data.

Whilst the data providers have attempted to compile registers which are both as complete and accurate as possible, there are data biases that should be considered. First, the electoral register (up to 2023) is known to sufficiently under-represent the following groups: the younger age groups, the non-white British population and those in rented accommodation. Second, the counts in the original data also fluctuated relative to the population growth. CDRC research subsequently attempted to fill in the gaps and reweight changes based on additional data sources.

The counts of households in the original LCR data fluctuate according to data supplier in addition to actual population size changes. As such, meta data describing the annual distribution of household counts across LSOAs and LADs for the 2023 baseline year that have been used in calculating RMI are available below. RMI may be out of line with census counts and users should consult census statistics if they have concerns. This is particularly pertinent to the last few years (2018-23), especially 2019, in addition to areas such as Braintree.

LAD Household Distribution (2023) - Min: 214, 1st Quartile: 16,423.25, Mean: 29,149.78, Median: 22,295.50, 3rd Quartile: 35,462, Max: 173,394, Standard Deviation: 21,206.49, Standard Error: 1,096.65.

LSOA Household Distribution (2023) - Min: 17, 1st Quartile: 195, Mean: 255.82, Median: 254, 3rd Quartile: 309, Max: 2109, Standard Deviation: 91.90, Standard Error: 0.45

The coverage and completeness of the LCR which have been used to create these data has gradually degraded in recent years, which may have resulted in a slight decline in the quality these derived data.