The HDI is a summary composite index that measures a country's average achievements in three basic aspects of human development:
* Health - measured by life expectancy at birth;
* Knowledge - measured by a combination of the adult literacy rate and the combined primary, secondary, and tertiary gross enrolment ratio;
* Standard of living - measured by GDP per capita (PPP US$).
The Human Development Report Offices strongly advises against constructing HDI trend analysis based on the HDI published in different editions of the Human Development Report. Due to revisions to the data series for some or all of the components of the HDI, changes in the HDI methodology, or variations in the country coverage, the HDI values and rankings presented in the 1990 through 2007/2008 editions of the Human Development Report are not directly comparable. For the most up-to-date HDI trend data based on consistent country coverage, methodology and data, use the table for years 1975,1980,1985,1990,1995,2000,2005