People sometimes wonder whether the countries which do well are more homogenous and have fewer ethnic divisions than ones which do badly. There are several points to keep in mind when considering this.  

First, an international study, which collected data on the ethnic mix in each country found that it did not explain the association between health and equality. Interestingly, a very similar proportion of the population of Sweden and the USA are foreign born, and Spain is more equal and does better than its neighbour, Portugal, despite having a larger migrant population.

Among the US states income distribution tends to be more unequal in states in which a higher proportion of the population are African-American. One paper suggested this explained the relation between inequality and health.  Since then other papers have been published showing this is not so and a computational error was found in the paper which first made that suggestion.  In addition, in the more unequal states health is worse among both the black and white populations. But migrant groups sometimes have unexpectedly good health. In the USA, the largest group of migrants are Hispanic, predominantly from Mexico.  Although their levels of education and income are much like those of African Americans, for most outcomes their health is as good as that of the non-Hispanic white population. That they do not seem to suffer the effects of their low social status is sometimes referred to as the ‘Hispanic paradox’.

However, insofar as ethnic divisions are related to inequality and may contribute to the effects of inequality, it is not of course skin colour itself – or for that matter religious or linguistic differences in themselves – which affect health. Instead, they become important when they serve as markers of social status attracting stigmatisation, prejudice and discrimination. This means that rather than ethnic divisions involving quite separate processes from those through which inequality has its effects, they involve very much the same processes.  Whether the markers of social status differences are attributes of class alone or whether they include issues of language, religion or ethnicity, the underlying processes are basically the same.