Reflecting inequality in each dimension of the HDI addresses an objective first stated in the Human Development Report 1990. The 2010 Report introduced the Inequality-adjusted HDI (IHDI), a measure of the level of human development of people in a society that accounts for inequality. Under perfect equality the IHDI is equal to the HDI, but falls below the HDI when inequality rises. In this sense, the IHDI is the actual level of human development (taking into account inequality), while the HDI can be viewed as an index of the potential human development that could be achieved if there is no inequality. The IHDI accounts for inequality in HDI dimensions by “discounting” each dimension’s average value according to its level of inequality measured by the Atkinson index.
We apply this index to 132 countries. Countries with less human development tend to have greater inequality in more dimensions—and thus larger losses in human development.