Cambridge is an urban area with a university, largely characterised by its big student population and high migration flows.
This brings challenges when estimating the population at a given time, meaning more timely and granular data are needed to provide the most accurate picture of Cambridge's population and to best direct services to meet needs across the area. The research showcased in this article shows how we can use administrative data alongside a wider range of data sources to achieve this.
All admin-based statistics in this article are referenced to mid-year, and Census 2021 statistics are referenced to March 2021. This may lead to some differences in the comparisons. The exception to this is the admin-based population estimates (ABPEs) (excluding Figure 3), which are compared with the Census 2021-based mid-year estimates.
Some statistics in this report are not official and should not be used for decision making. They are estimates based on new methodologies that are different from those currently used to produce official statistics. These outputs must not be reproduced without this warning.
Population and migration in Cambridge
The size and structure of the population in Cambridge is largely made up of young working-age individuals and students. These patterns are similar for admin-based population estimates (ABPEs) and census-based mid-year estimates (MYEs). Our ABPEs show that there were 143,800 people living in Cambridge in 2021. This increased by 1.7% to 146,200 in 2022 (Figure 2). The population was 49.8% female and 50.2% male.
Figure 1: Admin-based population estimates (ABPE) data show the largest percentage of people living in Cambridge were aged 19 to 23 years
Age structure of the population for mid-year estimates compared with ABPE, by sex, Cambridge, 2021
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- As Census 2021-based MYE is used as an input to the model, outputs are very similar to Census 2021-based MYE. There are small differences because the dynamic population model (DPM) balances the information available in population stocks and flows based on their respective measures of precision.
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Identifying movement of the population into and out of the area is also important for decision makers to understand the changing service needs, particularly during and after a special event such as the pandemic. Our ABPEs enabled us to see the change in population between 2021 (during various lockdowns) and 2022 (after lockdown) at least four months earlier than the current census-based system.
Figure 2: Cambridge's population increased by 1.7% to 146,200 people between 2021 and 2022
Admin-based population estimates (ABPE) percentage change in population, local authorities in England and Wales
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- City of London (plus 24%) and Isles of Scilly (plus 10%) have been omitted from the figure to show the distribution of all other areas more clearly across England and Wales.
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We are also able to understand more in local areas, such as Lower layer Super Output Areas (LSOA), by using administrative data on a regular basis to understand how the local populations are changing.
We have compared our ABPEs with Census 2021 estimates at LSOA level, with approximately 75% of LSOAs showing differences of within plus or minus 8% of the census estimates. There are greater differences between estimates than at local authority (LA) level in certain areas.
Our previous research shows these larger differences are often where there are communal establishments (CEs) with large, regularly changing populations concentrated in small areas, such as students in halls of residence or armed forces in military bases. These population groups are less likely to interact with services in a typical way and may not be captured at the same location as the census.
In addition to this, we see differences between census-based and admin-based estimates in areas with high levels of migration into and out of an area. This is because of differences in the reference period and the time taken to update administrative records following a move.
Figure 3: The largest difference in population estimates between ABPEs and Census 2021 were in LSOAs with communal establishments
Percentage difference in admin-based population estimates (ABPE) and Census 2021 estimates at Lower layer Super Output Areas (LSOA) level, Cambridge, 2021
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Notes
- Figures in this chart have used the Census 2021 estimates rather than our MYEs referenced in Figures 1 and 2. These have been used as a proxy since we are currently working on producing MYEs at local levels. For more information on this, please see our technical topic guide.
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Changes in Cambridge's daytime population
Understanding who or what behaviours are causing these population changes further supports decision-making around directing services. For example, an area may need more medical services if the population increases significantly during the day.
Looking at the changes in Cambridge's local area populations, we see certain areas experience higher population counts at certain points in the day, which we believe are accounted for by people travelling into and out of work or university.
To view how Cambridge's population changes over the day, please see Estimating the population by time of day.
To view work-related travel to and from small areas in Cambridge, please see Travel to work.
Population sub-groups and characteristics in Cambridge
Beyond the size and structure of the population, we can learn more about the make-up of the local areas and communities across Cambridge by examining the characteristics of those who live there. This will aid us in further understanding where inequalities may exist across the local areas in order to identify where additional support or services may be required.
Cambridge has a higher proportion of people identifying with each ethnic minority group (excluding "White" ethnic minorities when referring to ethnic minority group) in the admin-based ethnicity statistics (ABES) compared with the national figure ("White" accounts for 77.5% in Cambridge, compared with the English national average of 82.9%).
The distribution of ABES aligns with Census 2021, with each ABES estimate shown to be within 3.0 percentage points of the census estimate (excluding "White" where the value falls to 1.7 percentage points). They are not the same because of differences in the way the data are collected, such as using different classifications and differences in self-reporting. The ABES estimate for the "White" ethnic group has the largest difference compared with the census, being 3.0 percentage points higher. We have analysed and produced evidence on this higher proportion of the "White" ethnic group in our Developing admin-based ethnicity statistics for England and Wales: 2020 article.
Figure 4: The ABES proportion of ethnic groups in Cambridge is similar to Census 2021.
Admin-based ethnicity statistics (ABES) and Census 2021 population by five-category ethnic group, Cambridge, 2021
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We can learn more about our population and their service needs through disaggregating by characteristics such as age and sex. For example, to better understand healthcare needs we can explore the differences between the types of ageing populations across our local areas.
Figure 5 shows the age breakdowns of different ethnic groups. We see more diversity across the younger age groups compared with the older population groups. For the "White" ethnic group the proportion of those aged 16 years and under is approximately 70%, compared with at least 94% for those aged 65 years and over. Understanding the make-up in local areas helps inform future health provisions for areas like Cambridge.
These trends are similar to the overall Census 2021 ethnic group distribution and broadly comparable across the age groups.
Figure 5: Cambridge's younger age groups are typically more ethnically diverse than older age groups for both males and females
5.a. Admin-based ethnicity statistics (ABES), “White” ethnic group by age and sex, Cambridge, 2021
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5.b. Admin-based ethnicity statistics (ABES), all other ethnic groups by age and sex, Cambridge, 2021
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We can also learn about these differences at smaller local areas, including Lower layer Super Output Areas (LSOA). For more information on ethnic groups at LSOA level, please see our associated datasets, which include our updated figures for 2021. Please see our evidence of LSOA coverage by ABES in our previous Developing admin-based ethnicity statistics for England and Wales: 2020 article.
Using our admin-based income statistics (ABIS), we can form a more detailed picture of how the people of Cambridge are living, and understand any inequalities occurring at local levels.
Median occupied address net income is the income for people living at the same address, which we use as a proxy for households. In Cambridge, median occupied address net income (£30,619) is higher than for England overall (£27,269), for reference tax year ending 2018.
By looking at the variation at the LSOA level, we show that while this trend is true for most areas within Cambridge, there are pockets where the median occupied address net income is lower than the England average. This is important for local planners and service providers to better target their services. There are some caveats to be considered when analysing these trends, for example, 3.5% of occupied addresses in Cambridge have no recorded income on the administrative data. For more information, please see our technical topic guide.
Figure 6: Median occupied address net income is higher than the average for England across many local areas in Cambridge
Admin-based income statistics (ABIS) median occupied address net income (£), Cambridge, tax year ending 2018
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Admin-based income statistics uses the concept of occupied address to capture household income, grouping individuals who are recorded as living at the same address.
Figures assume that income is shared evenly between all occupied address members.
Net income is calculated by deducting Income Tax and National Insurance contributions (derived in accordance with HMRC guidelines) from gross income.
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Our admin-based income by ethnicity statistics (ABIES) estimate the net income for individuals aged 16 years and over with income information identified by five-category ethnic group. With an ethnically diverse population across the younger age groups and higher median occupied address income than the national average, we see this reflected in the wider distributions of the individual income distributions of the "White" and "Asian" ethnic groups in Cambridge (Figure 7). However, Figure 6 shows there are areas within Cambridge with lower occupied address incomes than the national average and this variation is reflected in the wide distributions shown in Figure 7. Further information on ABIES statistics, including explanations for the differences in the measures, can be found in our Developing subnational multivariate income by ethnicity statistics from administrative data article.
Figure 7: Income measures in the admin-based income by ethnicity statistics (ABIES) dataset for Cambridge show variation between ethnic groups
The 10th percentile, median, and 90th percentile net income for individuals aged 16 years and over with income information identified by five-category ethnic group, Cambridge, tax year ending 2018
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We are not yet able to determine how representative our analysis is of the total population and so these figures may not reflect the incomes of the underlying population and should be interpreted with caution.
We were able to identify 63.3% of records with both income information and a stated ethnicity.
For more information on the categories included, see our technical topic guide.
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Housing, housing characteristics and living arrangements in Cambridge
Looking beyond the individuals who make up our population, we have used administrative data to understand how people live together across local communities.
The census groups usual residents into households based on the self-reported use of shared facilities. Most residential addresses in England and Wales are used by a single household. In contrast, we report on occupied addresses because it is currently not possible to accurately identify multiple households at an address from administrative data alone. Addresses are most closely related to a self-contained dwelling definition. From the census, we estimate that this difference in definitions affects less than 1% of dwellings.
Our admin-based occupied address dataset (ABOAD) identified 48,700 occupied addresses in Cambridge in 2021 compared with 52,500 households in Census 2021. The ABOAD counts occupied addresses while the census counts households, so multiple households living at the same address will be counted individually for the census. This is not the only factor contributing to the difference, for example we have undercount in our underlying dataset and the base population. For more information, see our technical topic guide.
Figure 8: There are more Census 2021 households in Cambridge than occupied addresses in the admin-based occupied address dataset (ABOAD)
Number of occupied addresses in the ABOAD and households in Census 2021, Cambridge, June 2021
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Occupied addresses with one or two persons living there were the most common among occupied addresses across Cambridge in 2021. Census shows the same for households.
Figure 9: Most residential addresses in Cambridge have one or two people living there
Size of occupied addresses in the admin-based occupied address dataset (ABOAD) and households in Census 2021 by number of people living there, Cambridge, June 2021
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To further understand people's living arrangements, we can use our admin-based housing stock version 1.0 (ABHS V1.0) statistics. This may help housing planners and policymakers to better understand the characteristics of the dwelling stock in their area, and therefore better meet the future housing needs of residents. The ABHS currently provides the following housing characteristics:
accommodation type
number of bedrooms
number of rooms
number of bathrooms
build period
Figure 8 shows that ABOAD counts fewer occupied addresses than census households. This is reflected in the ABHS. When comparing Valuation Office Agency (VOA) estimates of number of rooms with Census 2021 data, figures differ based on whether we analyse all residential or occupied residential addresses. In Figure 10, we see how the ABHS shows a similar distribution to the census, with most addresses in Cambridge having between three and five rooms.
Figure 10: Dwellings in Cambridge most commonly have five rooms
Distribution of Census 2021 households by number of rooms, alongside the distribution of residential addresses and occupied residential addresses in the ABHS V1.0, Cambridge, 2021
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Notes
The admin based housing stock version 1.0 (ABHS V1.0) dataset counts addresses, while Census 2021 counts households, so multiple households living at the same address will be counted individually for the census.
In contrast to previous censuses, Census 2021 did not ask a question on number of rooms, but it used linked administrative data.
For more information on these different definitions see our technical topic guide.
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Knowing the age of dwellings in which residents are living allows us to further understand the features of our housing stock and plan for future need.
In Cambridge, 10,450 dwellings were built before 1919, but only 8,660 were found as being occupied in 2021 according to the ABHS V1.0.
Figure 11: A large proportion of Cambridge’s housing stock was built before 1919
Number of dwellings by Valuation Office Agency (VOA) build period for all addresses and occupied addresses in the ABHS V1.0, Cambridge, June 2021
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Using the admin-based housing by ethnicity dataset version 2.0 (ABHED V2.0), we can extend our understanding of the living arrangements of different ethnic groups across Cambridge. As an example, we have produced analysis on the accommodation type lived in by ethnic groups and the numbers of bedrooms in these dwellings.
In Cambridge, there are differences in the types of accommodation occupied by different ethnic groups, which are also reflected in the number of bedrooms.
While the most common accommodation type for all ethnic groups is terraced houses, individuals in the "Black" and "Other" ethnic groups are more likely than other ethnic groups to live in flats, and less likely to live in detached or semi-detached dwellings (Figure 12).
Figure 12: Terraced houses are the most common Valuation Office Agency (VOA) accommodation type for all ethnic groups in Cambridge
Admin-based housing by ethnicity dataset version 2.0 (ABHED V2.0) VOA Office accommodation type (Census 2021 definition) by ethnic group, Cambridge, 2021
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Notes
Data are by individuals and not by addresses.
Valuation Office Agency (VOA) accommodation type is a derived variable designed to align with the Census 2021 definition; for more information see our technical topic guide.
Figures have not been adjusted to account for differences in age structure or household size by ethnic group within the population.
Figures include supressed and rounded values, so some categories appear under or over 100%.
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Figure 13 shows that while the most common number of bedrooms for all ethnic groups is three, individuals in the “Black” and “Other” ethnic groups are less likely than other ethnic groups to live in dwellings with four or more bedrooms.
Figure 13: Individuals in the "Black" and "Other" ethnic groups are less likely to live in dwellings with four or more bedrooms compared with all other ethnic groups
Admin-based housing by ethnicity dataset version 2.0 (ABHED V2.0) VOA number of bedrooms by ethnic group, Cambridge, 2021
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Notes
Data represent individuals rather than addresses.
There are definitional differences between the number of bedrooms for census and the Valuation Office Agency (VOA) data used in the admin-based housing by ethnicity dataset: see the technical topic guide for more information.
Figures include suppressed and rounded values, so some categories appear under or over 100%.
Figures have not been adjusted to account for differences in age structure or household size by ethnic group within the population.
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Beyond the population living in private households, we can learn more about the characteristics of the population living in communal establishments (CEs). CEs are places with full or part-time supervision providing accommodation. These groups are challenging to capture in our population, so work has started to understand more about who is living there. With more frequently updated figures, we can capture how the population living in CEs changes over time and the impact this has on the service provision for local areas.
The admin-based communal establishment dataset (ABCED) shows that the total population living in CEs in Cambridge was 16,620, compared with 19,290 on the census. Of those found in CEs on administrative data, 93.2% lived in halls of residence.
| Communal establishment type | Percentage of usual residents | |
|---|---|---|
| Halls of residence | 93.2% | |
| Care homes | 3.6% | |
| Boarding schools | 1.7% | |
| Hostel/temporary shelter for the homeless | 0.8% | |
| Holiday accommodation | 0.6% |
Download this table Table 1: Across Cambridge, the largest percentage of communal establishment residents live in halls of residence
.xls .csvThrough disaggregating by age and sex, we see who makes up the population of residents in CEs across Cambridge.
Figure 14: The most common age group of communal establishment residents in Cambridge was those aged 16 to 24 years for both males and females
Admin-based communal establishment dataset (ABCED) communal establishment residents by sex and banded age groups, Cambridge, 2021
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Notes
The ABCED has a different reference period compared with the data used in the occupied address dataset, meaning they are not directly comparable.
Figures are not directly comparable to official Higher Education Statistics Agency (HESA) halls of residence figures as the base population only includes usual residents while HESA includes all registered.
These figures are not comparable to official Ministry of Justice data on residents in prison.
The ABCED includes raw figures and has not had additional estimation methods applied, unlike the official Census 2021 estimates.
Percentages have been calculated for the whole population, so each individual sex will not total 100%; this differs from previously published figures which are therefore not comparable.
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The analysis presented in this article shows how our admin-based statistics can support our understanding of the diverse and changing needs of the local communities across Cambridge. This demonstrates their potential and is just a subset of what users can expect from our future population and social statistics system.
For more information on the methodology behind the administrative data collections referenced previously, please see our technical topic guide.
To find out more about our progress towards a transformed population and migration statistics system, please see our research overview.