The HDI is an average measure of basic human development achievements in a country. Like all averages, the HDI masks inequality in the distribution of human development across the population at the country level. The 2010 HDR introduced the Inequality Adjusted HDI (IHDI), which takes into account inequality in all three dimensions of the HDI by ‘discounting’ each dimension’s average value according to its level of inequality. The HDI can be viewed as an index of 'potential' human development and the IHDI as an index of actual human development. The ‘loss’ in potential human development due to inequality is
given by the difference between the HDI and the IHDI, and can be expressed as a percentage. (For more details see technical note 2).