https://www.sciencedaily.com/releases/2018/11/181106111626.htm

Measuring the overall wellbeing of populations is crucial for evaluating the success of policies. The Human Life Indicator expresses wellbeing in terms of years of life, similar to life expectancy at birth. However, unlike any other current measure, it takes not only the mean value but also the inequality in longevity into account. The wide availability of mortality data means that the HLI can be used for reliable comparisons of wellbeing across countries, in the past as well as the present.

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.