Health, income, and measures of inequality : why inequality may decline when all inequality measures indicate the opposite

We study how measures of socioeconomic health inequality inform about welfare inequality. We argue that transfers of either income or health from a better off to a worse off individual should reduce welfare inequality. Lacking an objective measure of individual welfare, we suggest that such a transfer should reduce at least one measure of inequality: inequality in income, health or socioeconomic health. This puts restrictions on measures of socioeconomic health inequality, where a correlation between income and health meets the requirement, while the concentration index only meets the requirement in a statistical sense. Finally, we show empirically that changes in the concentration index over time can be dominated by changes in income. Using data from HUNT, income changes account for 90% of the changes in the concentration index, while health and income are equally important with data from EU-SILC, with large variation across countries and years.