The HDI is a simple average of three indicators: longevity, as measured by life expectancy at birth; educational attainment, as measured by a combination of adult literacy (two-thirds weight) and the combined gross primary, secondary and tertiary enrolment ratio (one-third weight); and standard of living, as measured by real GDP per capita (PPP$). One should note that when making comparisons of the HDI across time, the methodologies of the three indices that comprise it have changed somewhat from year to year.
Methodology of Sources for Indicators for the Caucasus and Central Asia