Making an estimate of the number of people and households for Output Areas in the 2001 Census

The 2001 Census of Population Key Statistics and Census Area Statistics contain a large number of tables for 233,060 Output Areas in the United Kingdom. Users of the data often want to use one number for the total population count for each area or one number for the total count of households. Because of the disclosure control measures applied, different tables may report different population or household totals. This article describes an investigation into the best way to estimate robust totals for people and households at Output Area level. We show that computing the average of people and household counts across the set of tables in which the same count appears is a good strategy. When we compare the mean or median person and household counts with those produced by summing from the postcode directory, the two sets of numbers are usually very close. Using averages in this way for other population bases in the sets of tables is therefore recommended. This technique can also be applied to larger areas.