Pré-publication, Document de travail: Individuals care not only about their own survival, but also about the survival of other persons. However, little attention has been paid so far to measuring the contribution of longer coexistence time to living standards. For that purpose, we develop a measure of coexistence time – the joint life expectancy -, which quantifies the average duration of existence for a group of persons. Then, using a lifecycle model with risky lifetime, we construct an equivalent consumption measure incorporating gains in single and joint life expectancies. An empirical application to France (1820-2010) shows that, assuming independent individual mortality risks, the rise in joint life expectancies contributed to improve standards of living significantly. We examine the robustness of that result to the introduction of dependent mortality risks using copulas, and we show that equivalent consumption patterns are robust to introducing risk dependence.