Life expectancy and happy life years
Life expectancy at birth is an estimate based on the prevailing conditions in the country, and is calculated through large-scale data collection of mortality rates at different ages.
Life expectancy is often regarded as a gold-standard measure of well-being. This is not simply because a long life is necessarily a good thing (although most people would probably say that it is, all else being equal), but because rates of life expectancy depend on numerous factors that relate directly to material conditions in a country. For instance, life expectancy at birth is extremely sensitive to the rate of infant mortality, which is itself a robust proxy indicator of access to sanitation and the state of healthcare. For these reasons, and undoubtedly thanks to its clarity and tangibility, life expectancy is widely used as a development indicator, and is one of the main components of the UN’s HDI.
As the ultimate end of society, the HPI uses a model combining longevity and subjective life satisfaction devised by the Dutch sociologist Ruut Veenhoven and dubbed happy life years (HLY) “the degree to which people live long and happily in a country at a certain time”. To calculate a nation’s mean HLY, ratings of life satisfaction are multiplied by mean life expectancy at birth. Veenhoven describes this as an “ultimate output measure”, because it incorporates both “apparent” and “assumed” quality of life. HLY correlates with factors such as affluence, education, political freedom and gender equality however, it is not completely explained by them. This suggests that the subjective component adds something distinctive that is not captured by purely objective measures of quality of life.