Attrition in Longitudinal Household Survey Data

Longitudinal household data can have considerable advantages over much more widely used cross-sectional data for capturing dynamic demographic relationships. However, a disturbing feature of such data is that there is often substantial attrition and this may make the interpretation of estimates problematic. Such attrition may be particularly severe where there is considerable migration between rural and urban areas. Many analysts share the intuition that attrition is likely to be selective on characteristics such as schooling and thus that high attrition is likely to bias estimates. This paper considers the extent and implications of attrition for three longitudinal household surveys from Bolivia, Kenya, and South Africa that report very high per-year attrition rates between survey rounds. Our estimates indicate that: (a) the means for a number of critical outcome and family background variables differ significantly between those who are lost to follow-up and those who are re-interviewed; (b) a number of family background variables are significant predictors of attrition; but (c) nevertheless, the coefficient estimates for standard family background variables in regressions and probit equations for a majority of the outcome variables considered in all three data sets are not affected significantly by attrition. Therefore, attrition apparently is not a general problem for obtaining consistent estimates 1 Development Research Group, World Bank, 1818 H Street NW, Washington D.C. 20433, USA. Email: [email protected]. 2 Population Studies Center, McNeil 160, 3718 Locust Walk, University of Pennsylvania, Philadelphia, PA 19104-6297, USA. Email: [email protected]. 3 Max-Planck Institute for Demographic Research, Doberaner Str. 114, 18057 Rostock, Germany. Email: [email protected]. 4 International Food Policy Research Institute, 2033 K Street NW, Washington D.C. 20006, USA. Email: [email protected]. 5 University of Pennsylvania, McNeil 113, 3718 Locust Walk, Philadelphia, PA 19104-6299, USA. Email: [email protected]. Demographic Research Volume 5, Article 4 80 http://www.demographic-research.org of the coefficients of interest for most of these outcomes. These results, which are very similar to those for developed countries, suggest that multivariate estimates of behavioral relations may not be biased due to attrition and thus support the collection of longitudinal data.