Keeping track of mobile families: characteristics, attrition and bias in the British birth cohort studies of 1970 and the millennium

Peter M. Shepherd, Institute of Education

Longitudinal datasets provide evidence about internal migration. The mobility of their subjects itself poses a major challenge Moving addresses is a major cause of survey attrition we want to know how movers differ from those who stay put. Both the 1970 and Millennium cohort studies in Britain have encountered high mobility among families with young children, so this paper will focus on methodological and substantive issues about moving home at this stage of the life cycle. We will present evidence from the 1970 cohort about mobility between the ages of 30 and 34 of cohort members with children across the age range, and, for the Millennium cohort, mobility for families with a young child for parents with a range of ages. We will also exploit the clustered nature of the Millennium sample to show how type of area relates to the mobility of families with young children.