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Fact check: What did the 2021 UK Census report about the Muslim population by local authority and age?
Executive Summary
The 2021 UK Census shows people identifying as Muslim are the youngest major religious group in England and Wales, with a median age of 27, and a large majority — about 84.5% — are under 50. The Census published age-by-religion breakdowns for multiple geographic levels, including local authorities, enabling comparisons of Muslim age profiles across places and revealing both a rise in the Muslim share of the population since 2011 (from 4.9% to 6.5%) and a modest ageing of the Muslim population (median age rising from 25 in 2011 to 27 in 2021) [1].
1. Why the Census headline matters — youthfulness and growth create planning demand
The Census headline that Muslims have the youngest median age [2] matters because age structure drives demand for services such as education, housing, and employment support; a younger population implies larger cohorts entering schools, universities and early-career labour markets. The 2021 tables also show that 84.5% of Muslims were under 50, concentrating population needs toward youth-oriented public policy, and the Muslim share of the population rose from 4.9% in 2011 to 6.5% in 2021, indicating not only a youthful profile but net growth in absolute and relative terms [1] [3]. The ONS and associated dataset releases explicitly provide these breakdowns by age and sex at national and local authority levels, enabling local planners to map age-specific service needs to geographic concentrations of Muslim residents [4] [3].
2. What the local authority tables actually show — granularity and use-cases
Census outputs include downloadable tables that classify usual residents by religion and age at local authority level, permitting analysts to see how the Muslim age profile varies across councils and metropolitan areas. The detailed datasets (including RM118 and related files) provide counts by age bands and sex for 10 religion categories and finer classifications, which researchers use to produce ward and local-authority level age pyramids and dependency ratios [4] [5]. Those files also note data protections and methodological notes, so users must consider sampling rules and disclosure control when examining small-area cells; the ONS guidance warns on interpreting very small counts and recommends aggregating age bands or areas where numbers are low [6].
3. How age changed since 2011 — modest ageing within a still-young group
Comparing 2011 and 2021, the Muslim population has aged slightly, with the median rising from 25 to 27, but it remains the youngest major group in the country. The Census commentary highlights that while the group’s median age increased, the overall growth from 4.9% to 6.5% means the younger structure still dominates population dynamics, reflecting higher proportions of children and young adults relative to older age groups [1] [3]. Analysts caution that small shifts in median can reflect both demographic ageing and changes in migration and fertility patterns; the published tables allow decomposition by age bands to examine whether ageing reflects cohort movement into older age bands or changes in the relative size of younger cohorts [5].
4. Sources, datasets and what to watch when comparing places
The principal releases are the ONS Census reports and the RM118/“Detailed religion by age and sex” datasets provided via the UK Data Service and ONS pages; these are the authoritative sources for the claims about median age, under-50 share, and local-authority breakdowns [1] [4] [5]. Users comparing local authorities should use the same age-band definitions and consider disclosure controls that suppress small counts; the dataset metadata and technical notes explain geography files, age categories, and the 21 March 2021 Census Day reference date used for the estimates [3] [6]. For robust local comparisons, aggregate adjacent age bands or areas with small Muslim populations to avoid misleading percentage swings driven by small denominators [5].
5. What the numbers don’t say — context and alternative explanations to consider
The Census provides a snapshot of identity and age but does not by itself explain drivers such as fertility, recent migration, or differential mortality that produce a younger Muslim profile; analysts must combine Census age-by-religion tables with birth, migration and cohort data to attribute causes. The published datasets include age and sex breakdowns but omit variables like country of birth or migration timing in the same table, so researchers often link separate tables or use longitudinal sources to unpack whether growth and youthfulness reflect recent arrivals, higher fertility, or historically younger family structures [4] [5]. Policymakers should therefore treat the Census age-by-religion findings as a foundational descriptive fact while pursuing deeper causal analysis with complementary data.