be the case. A spectacular example is provided by the recently devised international development goals (IDGs) (International Monetary Fund and others 2000), which are being used to monitor the success of international development assistance (e.g., grants, credits, loans, debt relief) through bilateral and multilateral aid programs. Targets for health outcomes feature prominently in the list of IDGs, but without exception the focus is on population averages. There has been virtually no discussion (Gwatkin 2000) of the possibility that progress toward the IDGs might be accompanied by a widening the gaps in, say, child mortality rates between poor and better-off children.

The IDGs notwithstanding, there is growing interest in and concern over socioeconomic inequalities in health in the developing world. Several key international organizations in the health field-including the World Bank (World Bank 1997) and the World Health Organization (World Health Organization 1999)-have stated the improvement of the health outcomes of the world's poor as their primary objective. So too do several bilateral donors, including the British government's Department for International Development (Department for International Development 1999). The growing interest within the international development community in improving the health of the world's poor reflects the ever broader interpretation being given to the term "poverty" in the academic literature (Sen 1999) and elsewhere, and the increasing tendency of aid agencies and nongovernmental organizations to define their goals in terms of poverty reduction. This is much in evidence in the World Bank's own work. Poverty reduction was adopted during the 1990s as the overriding mission of the organization, and especially following the publication of the latest World Development Report (World Bank 2000) has been interpreted broadly in multidimensional terms. But the increasing focus on the health of the world's poor also reflects a growing consensus that inequalities in health outcomes between rich and poor are unjust-whether they be between the people of, say, Sierra Leone and Sweden, or between, say, poor Bolivians and better-off Bolivians. Closing intercountry and intracountry gaps between the poor and better-off, by securing greater proportional improvements among poorer groups, is not simply a poverty issue-it is also a question of social justice and equity (Alleyne, Casas, and Castillo-Salgado 2000; Wagstaff 2001). Indeed, it is this, rather than the emphasis on poverty reduction, that has kept the debate on socioeconomic inequalities in health so buoyant in many of the European countries, and it is this that appears to be pushing the issue ever further to the forefront of the debate on development assistance in these countries.

But how large are socioeconomic inequalities in health in the developing world? Are they higher in some countries than others? If so, what factors account for these higher inequalities? The paper begins with the presentation of some data on child health inequalities in 42 countries. The inequalities reported are sometimes large, sometimes fairly small, and they vary considerably across countries. The paper then goes on to outline a simple stylized model that might help explain this variation in health inequalities across countries. Three factors are hypothesized to be central-differences in incomes per capita; differences in income inequalities; and differences in policies that influence how much people pay out-of-pocket for their health care. These hypotheses are then tested on the data for the 42 countries. Surprisingly, little evidence is found in support of the hypothesis that _2_