About the data
The Millennium Cohort Study (MCS) is the 'youngest' of the birth cohort studies that have been conducted in Britain, and has followed almost 19,000 children born in 2000-2001. Interviews have been conducted with parents/guardians when the child reached 9 months, three years, five years and seven years - with a fourth interview planned for when the children are aged 11 (and in their last year of primary school). Unlike past birth cohorts, the attention has been on relatively 'social' rather than 'medical' issues even from the early interviews. The sample was also taken from throughout the year, rather than a single week which was the practice with the 1958 and 1970 cohorts.
How the data were used
The aim of this study, 'The consequences of raising twins', planned in collaboration with the Twins and Multiple Birth Association (TAMBA), was to consider how having twins affected parental resources and child outcomes.
There have been several studies that have looked at twins as research subjects, and in particular as a means of looking at the balance of 'nature' and 'nurture' on different outcomes, such as intelligence or social mobility. It has been much less common to look at the effects on families of having twins (or higher order multiple births).
A range of relevant information within the MCS was identified such as rates of employment, hours of work, marital status, subsequent fertility and incomes. It was also necessary to control for different features of the family, as those having twins tend to be older than average, and to already have children. The research found that having twins was associated with lower incomes and higher levels of parental stress, the former resulting, in part, from lower rates of female work participation among those with multiple births.
About the author
Stephen McKay is Professor of social research at the University of Birmingham. He has particular interests in the analysis of living standards, incomes and poverty, and in applications of quantitative methods within the social sciences. He often works with large-scale and longitudinal data from the UK Data Archive.
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