Changing age-specific fertility in England and Wales: understanding the fertility of recent migrants

James Robards, University of Southampton

The Office for National Statistics Longitudinal Study (LS) for England and Wales is a large, dataset of linked census and vital event information composed of a 1% sample of the population. The LS is potentially a suitable dataset for understanding the fertility of recent migrants to England and Wales, as through registration with a General Practitioner new migrants are added to the LS. However, it is known that data on migration, especially on emigration (or embarkation), is not always recorded in the LS. Therefore, although because of the large sample size that this dataset offers for analysis there has been a tendency for researchers to assume that the LS is representative of the population of England and Wales, this is unlikely to be the case. For example reports produced by the Office for National Statistics show that there is a lower rate of census-to-census linkage for specific members of the LS. Building on existing knowledge, this paper hypothesises idealised residence ‘trajectories’ for female LS members in the 1991-2001 period. LS members are attributed to each of the trajectories created and hence we are able to estimate the proportion of LS members who have incomplete information, for example because they make an unrecorded embarkation from the LS in the 1991-2001 period. The various residence trajectories are used to calculate numbers of women in the LS who are exposed to risk of giving birth, and the number of births to these women in the LS. Hence we estimate fertility rates for women according to their residence trajectories. Through the accurate calculation of the numbers of women exposed to risk of birth it is possible to understand precise residence trajectories and subsequent fertility for LS members who migrated to England and Wales.