Which of the following indicators is NOT used to calculate Human Development Index (HDI) ?

The correct answer is D. The HDI, introduced by UNDP in its 1990 Human Development Report, rests on three dimensions: a long and healthy life, knowledge, and a decent standard of living. Social inequality is not a component of the basic HDI.

• A (Life Expectancy): This is the health dimension, measured by life expectancy at birth. It is part of HDI, so this is a wrong option.
• B (Education): Measured by mean years of schooling and expected years of schooling. Part of HDI, so this is a wrong option.
• C (Per Capita Income): This is the living standards dimension. It was earlier measured by GDP per capita (PPP) and, since the 2010 methodology revision, by GNI per capita (PPP). Part of HDI, so this is a wrong option.
• D (Social Inequality): Not part of HDI. Inequality enters only through the Inequality-adjusted HDI (IHDI), which is a separate index, and through the Gender Inequality Index and the Multidimensional Poverty Index, which are also separate measures.

Core concept: composite indices and how they are constructed. Mains angle: why GDP alone misses well-being, and how HDI shifted the development debate from growth towards capabilities, an idea closely linked to Amartya Sen's capability approach.

Trap: aspirants see the word 'inequality' and assume the HDI is inequality-adjusted, so they pick a wrong option. The adjusted version (IHDI) is a different index.