The Area Level Index of Age Diversity (ALIAD) is based on the Simpson's Index of Diversity. It is commonly used in ecological studies to quantify the biodiversity of a habitat as it takes into account both the richness, i.e. the number of species present, and the evenness, i.e. the abundance of each species, within an environment. As species richness and evenness increase, so diversity increases. The index represents the probability that two randomly selected individuals will belong to different groups. It ranges from 0 and 100, with higher values representing greater diversity. ALIAD was computed for each Lower Super Output Area (LSOA) in England and Wales (E&W), each Data Zone (DZ) in Scotland and each Super Output Area (SOA) in Northern Ireland from 2002 to 2019. It is based on the mid-year population estimates (MYPE) for each area for each year. This is information is freely available in accordance with version 3.0 of the Open Government Licence. However, the different national statistical agencies compute MYPE for different age groups. In England and Wales estimates are provided for single-year age groups, i.e. the number of people aged 0, 1, 2, 3, etc. In Scotland estimates are provided for quinary age groups, i.e. the number of people aged 0-4, 5-9, 10-14, etc. In Northern Ireland (NI) estimates are provided for four larger age groups, i.e. 0-15, 16-39, 40-64 and 65+. It was decided to match the age groups to the NI classification as i) this would provide the greatest geographical coverage, ii) the estimates ought to be more robust and iii) in discussions with policy and practice stakeholders these age groups were seen as more meaningful than single-year or quinary age groups. An exact match was possible between the E&W and NI age groups. However, because of the use of quinary age groups it is not possible to get an exact match for all age groups in Scotland. Hence, the age groups used on Scotland are 0-14, 15-39, 40-64 and 65+. The final dataset contains the computed ALIAD values for each of the 34,753 LSOAs, the 6,976 DZs and the 890 SOAs from 2002-2019. ALIAD has a range of 0-100. On this scale 0 would represent total age concentration, i.e. every member of the area is in the same age group, and 100 would represent complete age diversity within the area.There is evidence that Britain is becoming more and more generationally divided. A major part of this is that the places where we live have become increasingly 'age segregated'. This means younger people tend to live in places where there are more younger people and older people tend to live in places where there are more older people. Deep generational divisions can have implications for social cohesion and effective societal functioning. Policy makers are concerned that this could have negative health, economic, social and political costs. Indeed, a recent report by the Resolution Foundation estimated that age-segregation could cost the UK economy £6 billion per year. However, there is currently no research in Britain that has been able to directly test whether living in areas with a greater mix of ages has an impact on people. By linking information on the number of people in different age groups at the local level with information from a long running survey, our project will be the first to do this. We will create a new measure, called the 'area level index of age diversity', for all the residential areas in Great Britain (these are called Lower Super Output Areas in England and Wales and Data Zones in Scotland). Unlike existing measures which tend to focus just on younger versus older adults, this new measure will use information from people of all ages to get a better idea of the mix of age groups in an area. The first thing we intend to do with this information is to produce a series of maps of Britain to show which local areas are more or less age diverse. This information will be very useful for local government, councils, city planners and the like. Once we have done this, we will then link our new measure of age diversity to information on around 50,000 people living in Britain who have been part of a long running study (called the UK Household Longitudinal Survey). This will enable us to see whether living in areas that have people from a wide (or narrow) range of age groups impacts on people's health (e.g. whether the person has an illness or chronic condition), well-being (e.g. loneliness), civic participation (e.g. whether someone volunteers or not), and neighbourhood quality (e.g. whether people trust their neighbours). Our findings will provide a much needed evidence base on the extent of local area level age diversity in Britain and what effect (if any) this has on people's lives.

ALIAD was computed for each Lower Super Output Area (LSOA) in England and Wales (E&W), each Data Zone (DZ) in Scotland and each Super Output Area (SOA) in Northern Ireland from 2002 to 2019. It is based on the mid-year population estimates (MYPE) for each area for each year.