The Office for National Statistics has used a new statistical disclosure control methodology for Census 2021. As a result, figures created by summing lower-level geographies will not match figures released for higher geographies. The Office for National Statistics does not recommend the aggregation of lower-level geographies to create higher geographies.

Furthermore, the statistical disclosure control methodology used by the ONS results in totals that are not consistent across all breakdowns and variable selections. To make sure we use consistent denominators across all Census rates and percentages displayed in InfoBaseCymru, we have calculated these using the same set of population and household figures.