To an extent the differences in ethnic composition identified in the comparison between the ALSPAC ‘enrolled sample’ and the national NPD KS4 GME sample can be attributed to regional differences and demographic changes within the UK since the birth of the cohort. The 1991 census data report that 4.1% of mothers with infants <1 year of age resident in Avon, described themselves as ‘non-White’, compared with 7.6% of mothers across the whole of Britain. Nationally, 14.0% of pupils in the NPD KS4 GME data are described as non-White compared with 8.0% of pupils regionally. In economic terms, the South West of England, which incorporates the ALSPAC catchment area, has a similar gross disposable household income per head (£13 300) to the English average (£13 500). This, however, masks regional differences; using the same measure, the South West ranks fourth highest of the 12 UK regions.6
