Survey evidence that provides a 'snapshot' picture of the current state of a population is commonplace. But many of the most pressing questions facing policymakers concern changes in states, or sequences of successive states, or the duration in particular states. What are the defining characteristics of people who experience repeated spells of unemployment? What is the impact of both parents working on children's subsequent development? Finding answers to questions like these requires evidence of a different sort: data describing the same people repeatedly at successive points in their lives. The value for policymakers and private sector decision-makers of longitudinal data and analysis is illustrated here by an example central to current policy discussions of family life, the dramatic growth in the number of births outside marriage.
In 1999, 39 per cent of births in Britain were outside marriage, a rise from nine per cent in 1975. There has been a tendency in the press and public discussion to call the mothers of these babies single mothers, suggesting that almost four out of ten children are now born into single parent families. This would be worrying because, as discussed here, there is growing evidence that experience of life in a single-parent family during childhood is usually associated with disadvantageous outcomes as young adults.
But other features of the birth registration statistics suggest that this may be a gross overstatement of births to single mothers. Four out of five births outside marriage are now jointly registered by both parents. The proportion of births outside marriage registered by the mother alone has declined while jointly registered births have increased.
...there is growing evidence that experience of life in a single-parent family during childhood is usually associated with disadvantageous outcomes as young adults.
For a majority of jointly registered births, the meaning of joint registration is relatively clear. Nearly 80 per cent of all jointly registered births outside marriage in 1998 were to parents living at the same address. These can be plausibly interpreted as births to a couple in a cohabiting union, and so it appears that about one in four recent births are in cohabiting unions, and about one in six births are to women not in a live-in partnership - true single mothers. Does this mean that the rise in extra-marital births should be much less of a cause for concern?
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