Births to Sample Mothers

Births to LS women are generated from England and Wales (E&W) birth registration data by using confidential particulars collected on the birth registration draft, which is completed by the informant (normally one of the parents) when registering either a live or a stillbirth. The informant is asked to state the mother’s date of birth; if this is one of the LS dates, the birth registration is then matched to the LS mother.

If there is a discrepancy between the mother's birth date given at the census or at immigration and that given when registering the birth of a child, then no linkage can be made between the LS member and the birth.

Methods

The LS includes linked census and events data for people born on one of four selected dates in a calendar year. As such, the LS samples 4/365 of people born in non leap years and 4/366 of people born in leap years. This represents approximately 4/365.25 of the population resident in England and Wales in any given year. The number of expected births to LS mothers in any year will be given by FIGURE 1.

In census years, the above formula uses the estimated numbers of England and Wales births from the start of the year up to the day before census night (pre-census) and from the day after census night until the end of the year (post-census). This allows us to derive one pre and one post-census estimate of expected births to LS mothers.

Results

Total numbers of births to LS mothers after the 2001 Census are shown in table 4.1 together with the relevant sampling fractions and linkage rates.

Table 4.1. Births to LS mothers by year of birth, 2001-2005,

Between 2001 and 2005, the sampling fractions and the linkage rates were very close to their respective 1.1 and 100 targets. This represents a substantial improvement from previous decades, when births to sample mother were under-sampled in the LS (see table 4.2).

Table 4.2. Births to LS mothers by decade of birth, 1971-2005,

Further breakdowns of sampling fractions and entry rates for births to LS mothers since 1971 are available from the Downloads section.

Figure 1