In the 2010 Human Development Report a further Inequality-adjusted Human Development Index (IHDI) was introduced. While the simple HDI remains useful, it stated that "the IHDI is the actual level of human development (accounting for inequality)" and "the HDI can be viewed as an index of “potential” human development (or the maximum IHDI that could be achieved if there were no inequality)".
Countries fall into four broad human development categories, each of which comprises 47 countries: Very High Human Development, High Human Development, Medium Human Development and Low Human Development (46 countries in this category).
Because of the new methodology adopted since the 2010 Human Development Report, the new reported HDI figures appear lower than the HDI figures in previous reports.
From 2007 to 2010, the first category was referred to as developed countries, and the last three are all grouped in developing countries. The original "high human development" category has been split into two as above in the report for 2007.
The country with the largest decrease in HDI since 1998 is Zimbabwe, falling from 0.514 in 1998 by 0.140 to 0.374 in 2010. The country with the largest decrease since 2009 is Cape Verde, which decreased by 0.170.
Over half of the world's population live in countries with "medium human development" (51%), while less than a fifth (18%) populate countries falling in the "low human development" category. Countries with "high" to "very high" human development account for slightly less than a third of the world's total population (30%).
The only year without a Human Development Report since 1990 was 2012. The latest report was launched on 24 July 2014 in Tokyo.