Standard statistical techniques have been used to measure how much the 2011 Census has undercounted, to adjust the results and to help more accurately assess the characteristics of individuals and households.
All census population estimates were extensively quality assured using other national and local sources of information.
The 2011 Census achieved its overall target response rate of 94% of the usually resident population of England and Wales, and over 80% in all local authorities. The population estimate for England and Wales of 56.1 million is estimated with 95% confidence to be accurate to within +/- 85,000 (0.15%).
Simultaneous but separate censuses took place in Scotland and Northern Ireland. These were run by the National Records of Scotland (NRS) and the Northern Ireland Statistics and Research Agency (NISRA) respectively.
Suppression rules and disclosure control
In order to protect against disclosure of personal information, records have been swapped between different geographic areas. Some counts will be affected, particularly small counts at the lowest geographical level.
Related publicationsQuality and methodology information
Further technical information
2011 Census information on The Office for National Statistics website