Which of the following is not a measure of Human Development Index?

Concept — The Human Development Index (HDI) is a composite index published by the UNDP in its Human Development Report. It summarises average achievement in three basic dimensions of human development: a long and healthy life, access to knowledge, and a decent standard of living. Each dimension is captured by its own indicator, each indicator is normalised into a dimension index, and the three dimension indices are combined into a single HDI value between 0 and 1.

Application — So the test for any statistic is simple: does it serve as an indicator of one of those three dimensions? Placing each listed statistic against the three dimensions gives:

Cross-check — The third dimension, a decent standard of living, is measured by per-capita income (GDP per capita at PPP in the original methodology, GNI per capita at PPP since 2010) — a statistic that is not offered here at all. Sex ratio, the number of females per 1,000 males, is a Census statistic describing the gender composition of a population; it is reported nationally and state-wise to track gender balance, but it is not an indicator of any of the three HDI dimensions.

A note on methodology — The 1990–2009 HDI measured the education dimension using adult literacy rate (two-thirds weight) together with the combined gross enrolment ratio (one-third weight), which is the framework this question follows. Since the 2010 Human Development Report the education dimension has instead used mean years of schooling and expected years of schooling. Under either framework the health dimension stays life expectancy at birth, and sex ratio has never been an HDI indicator.

Result — The statistic that is not a measure of the Human Development Index is Sex Ratio.