Does the measure of economic disadvantage matter? Exploring the effect of individual and relative deprivation on intrauterine growth restriction

This paper examines the relation between health, individual income, and relative deprivation. Three alternative measures of relative deprivation are described, Yitzhaik relative deprivation, Deaton relative deprivation, and log income difference relative deprivation, with attention to problems in measuring permanent disadvantage when the underlying income distribution is changing over time. We used data from the National Longitudinal Surveys of Youth, a US-based longitudinal survey, to examine the associations between disadvantage, measured cross-sectionally and aggregated over the life course, and intrauterine growth restriction (IUGR). We reject the hypotheses that any of the economic measures, whether permanent/contemporaneous or individual/relative, have different associations with IUGR in terms of sign and significance. There was some evidence that permanent economic disadvantage was associated with greater risk of IUGR than those on the corresponding contemporaneous measures. The fitted values from logistic regressions on each measure of disadvantage were compared with the two-way plots of the observed IUGR-income pattern. Deaton relative deprivation and log income difference tracked the observed probability of IUGR as a function of income more closely than the other two measures of relative deprivation. Finally, we examined the determinants of each measure of disadvantage. Observed characteristics in childhood and adulthood explained more of the variance in log income difference and Deaton relative deprivation than in the other two measures of disadvantage. They also explained more of the variance in permanent disadvantage than in the contemporaneous counterpart.