Tarek Mostafa, Institute of Education - University of London - Department of Quantitative Social Science - Centre for Longitudinal Studies.
Richard D. Wiggins
BCS70, attrition, unit non-response, item non-response, weights, imputation.
The 1970 British Cohort Study (BCS70) is a continuing multi-purpose, multidisciplinary longitudinal study based on a sample of over 17000 babies born in England, Wales and Scotland. The study has collected detailed information from main parents then cohort members on various aspects of their family circumstances at birth, on their education, employment, housing and partnership histories over eight subsequent sweeps of data collection at ages 5, 10, 16, 26, 30, 34, 38 and most recently age 42 (2012). This paper studies the extent of attrition in BCS70 and how it affects sample composition over time. We examine the determinants of response then construct inverse probability weights. In the last section, we use a simulation study to illustrate the effectiveness of weights and imputations in dealing with unit non-response and item missingness respectively. Our findings show that when the predictive power of the response models is weak, the efficacy of non-response weights is undermined. Further, multiple imputations are effective in reducing the bias resulting from item missingness when the magnitude of the bias is high and the imputation models are well specified.