Cross-sectional weighting of longitudinal surveys of individuals and households using the weight share method

Statistical agencies are conducting increasing numbers of longitudinal surveys. Although the main output of these surveys consists of longitudinal data, most of them are also expected to produce reliable cross-sectional estimates. In surveys of individuals and households, population dynamics significantly changes household composition over time. For this reason, methods of cross-sectional estimation must be adapted to the longitudinal aspect of the sample. This paper discusses in a general context the Weight Share method, of which one application is to assign a basic weight to each individual in a household. The variance estimator associated with the Weight Share method is also presented. The weighting of a longitudinal sample is then discussed when a supplementary sample is selected to improve the cross-sectional representativeness of the sample. The paper presents as an application the Survey of Labour and Income Dynamics (SLID) introduced by Statistics Canada in 1994. This longitudinal survey covers individuals’ work experience, changes in income and changes in family composition.