Which three variables does HDI consider to measure development?

The Human Development Index (HDI) is a composite statistic used to measure a country's social and economic development. It specifically incorporates three critical variables:

1. GNI per capita: This variable measures the average income earned by each individual in a given country, adjusted for purchasing power parity. It provides a gauge of the economic prosperity and wealth distribution within a nation.

2. Life expectancy at birth: This is a health measure indicating the average number of years a newborn is expected to live based on current mortality rates. It reflects the overall health and longevity of a country's population and is influenced by factors such as healthcare quality, nutrition, and living conditions.

3. Education: HDI incorporates education by looking at mean years of schooling for adults aged 25 and older, as well as expected years of schooling for children. This metric reflects the access to and quality of education available to the population, which is crucial for individual development and economic growth.

These three components—economic status (GNI per capita), health (life expectancy), and education—are pivotal in assessing human development comprehensively. The other options do not encompass all three crucial aspects that HDI evaluates, making this selection the most accurate.