The Census provides a wealth of information about migration in the UK in the year before the Census, and about workers and their workplaces at the time of the Census. There is simple information at the most detailed geographical level, with more detail for larger populations.
The complete sets of information each have three components. First, there are figures about in migrants or workers in their areas of residence Second, there are figures about out migrants from an area or people with workplaces in an area. (An 'in migrant' had a different address one year before the Census, whilst an 'out migrant' was resident in the area one year before the Census but was resident elsewhere in the UK at the time of the Census.) Third, there are figures about flows of migrants or workers between areas. The first two components are in the standard area statistics, and can be used with them without additional preparation. The third component - the flows - are supplied separately, and require special preparations for use.
Migration and workplace in the standard area statistics
Information about in migrants and about workers resident in an area is in the Key Statistics, Census Area Statistics, and Standard Tables. Information about out migrants and about people with workplaces in an area is similarly available in the Key Statistics, Census Area Statistics and Standard Tables. This information is available for most but not all of the areas for which the standard output has been prepared. It enables many types of analysis, and if necessary the data can be manipulated with the software provided with the products or with other general software packages.
Flows of migrants and workers
The flows of migrants and the daily flows of workers from residence to workplace are provided as matrices of all areas of origin to all areas of destination at a specific geographical level. These are Output Areas, wards and local authorities with boundaries as at 31 December 2002. There are counts of every area to area flow (each cell in the matrix), with breakdowns of the characteristics of the people in the flow, and with more detail for the higher geographical levels. The matrices are large files and analysis requires the use of specialist software, which is not supplied by the Census organisations but which is available from intermediary organisations [for more information, contact Census Customer Services].
Differences in the UK
Most of the flow information is available as standard throughout the UK, but there are some differences in the tables provided for each part of the UK. Parliamentary constituencies are included in place of local authorities in Northern Ireland, and some information is available for postcode sectors in Scotland.
A separate set of tables on journeys to place of work or study is also available for residents of Scotland alone (a question on place of study was not included in the Census forms for the rest of the UK).
Guidance on use
All 2001 Census migration and workplace information is presented on the basis of estimates for 100 per cent of the population, which in particular has improved the accuracy of the workplace information compared with the 10 per cent sample used for the 1991 and earlier Censuses. This involved the coding of all 'remote' addresses (previous addresses and workplaces) on the forms and the imputation of missing addresses.
Migrants and workers are sub sets of the population as a whole, and, as numbers in migration and workplace flows generally decrease with greater distance of move, many of the counts in the cells of the matrices are very small, and indeed the majority are nil when the lowest geographical levels are included. The recording and capture of 'remote' addresses is also subject to error. It is therefore necessary to use the information with caution to allow for variability, generally by using the largest populations commensurate with a particular analysis. The fact that information is provided for all cells of the matrix at three main levels of geography gives the necessary flexibility to use larger areas and/or to group populations.
It is also necessary to take account of the effects of small cell adjustment applied as a disclosure protection measure, particularly when numbers in flows drop over longer distances.
Workplace and migration flows
The information, produced jointly by the three UK Census organisations, is available on CD or DVD from Census Customer Services, normally without charge, as four separate products - three combining migration and workplace flows for a specific level of geography, and the fourth with additional information on migration at local authority and ward levels.