HernĂ¡n Vallejo2026-03-222026-03-22202410.2139/ssrn.4830985https://doi.org/10.2139/ssrn.4830985https://andeanlibrary.org/handle/123456789/75174enSpan (engineering)WelfareEconomicsEconometricsPublic economicsA Theory of Lifetime Welfare: Cycles, Trend, Span, and Policiesarticle