How lifespan and life years lost equate to unity

Abstract

BACKGROUND Life expectancy at birth ( e 0 ), life years lost at death ( e † ), and lifetable entropy ( H ) are key indicators that capture average lifespan and lifespan variation. Expressions and relationships among these summary measures form the basis to analytically derive a range of formal demographic relationships, that build on each other and together help create new insights. Even though many elegant relationships are known, new ones are still to be discovered.