Years of Life Lost

Years of life lost (YLL) measures the burden of premature mortality by counting, for every death, how many additional years the person could have expected to live had they survived to a reference life expectancy. Summed over all deaths, YLL turns a count of deaths into a count of lost life-years, so that deaths at young ages weigh far more heavily than deaths in old age. It is the mortality half of the disability-adjusted life year (DALY) and a core metric of the Global Burden of Disease studies, letting analysts rank diseases and injuries by how much potential life they destroy rather than merely by how many people they kill.