Measuring family socioeconomic status: An illustration using data from PIRLS 2006

Many analyses of educational outcomes include a single socioeconomic status (SES) index as a predictor or for statistical control. In large-scale assessment research, these analyses have primarily examined the influence of SES on academic achievement in schools and the influence of other individual, family, and school variables when controlling for SES. The findings have helped elucidate the mechanisms underlying the influence of SES and identify possible avenues for reducing it. The measurement of SES is critically important with respect to the findings and implications of these analyses. This paper demonstrates a step-bystep procedure for calculating a family SES index using data from the Progress in International Reading Literacy Study (PIRLS) 2006. Variables reflecting parental education, parental occupational status, and family wealth were reduced into a single SES index using principal component analysis (PCA). The conceptual definition of SES, its reliability and crossnational comparability are discussed, and recommendations for further research and survey developers are offered. The presented procedure can be extended to other large-scale studies of educational achievement. Its illustration is the main contribution of this paper.