Inequalities in health have recently started to receive a good deal of attention in the developing world. But how large are they? And how large are the differences across the countries?

Recent data from a 42-country study shows large but varying inequalities in health across countries. Wagstaff explores the reasons for these inter-country differences and concludes that large inequalities in health are not apparently associated with large inequalities in income or with small shares of publicly financed health spending. But they are associated with higher per capita incomes.

Evidence from trends in health inequalities - in both the developing and the industrial world - supports the notion that health inequalities rise with rising per capita incomes. The association between health inequalities and per capita incomes is probably due in part to technological change going hand-in-hand with economic growth, coupled with a tendency for the better-off to assimilate new technology ahead of the poor.

Since increased health inequalities associated with rising per capita incomes is a bad thing and increased average health levels associated with rising incomes are a good thing, Wagstaff outlines a way of quantifying the tradeoff between health inequalities and health levels. He also suggests that successful anti-inequality policies can be devised, but that their success cannot be established simply by looking at "headline" health inequality figures, since these reflect the effects of differences and changes in other variables, including per capita income.

Wagstaff identifies four approaches that can shed light on the impacts of anti-inequality policies on health inequalities: cross-country comparative studies, country-based before-and-after studies with controls, benefit-incidence analysis and decomposition analysis. The results of studies based on these four approaches do not give as many clear-cut answers as one might like on how best to swim against the tide of rising per capita incomes and their apparent inequality-increasing effects. But they ought to at least help us build our stock of knowledge on the subject.