https://phys.org/news/2018-11-wellbeing-populations-human-index.html

Imagine an extreme case where half of the population live until they are 90 years old, but the other half die at age 30. The life expectancy of that population will be 60 years—the same as in the arguably better situation in which all members of the population lived to become 60. The HLI can distinguish between these two cases: If all members of the population live to the same age, in this case 60 years, the HLI equals 60. In the case of above where half the population dies at age 30, however, the HLI would be reduced to 52.

Early attempts to quantify wellbeing focused solely on economic factors, such as the Gross National Income per capita. In 1990, the UN added two additional dimensions, education and life expectancy, to create the more comprehensive HDI. Despite it being criticized due to statistical and conceptual flaws, the HDI is still widely used today.