The effective life span, or quantity of life, of an altruistic parent extends beyond her own longevity. The quantity of life is also determined by the number and longevity of her descendants. Using a calibrated version of the Barro–Becker model, I derive and estimate measures of effective quantity of life and of relative well-being for representative individuals of 116 countries between 1970 and 2005. I find that the gains in effective quantity of life arising from longevity improvements were on average more than offset by the losses due to fertility reductions. Effective quantity of life in the world fell by more than 7 percent during the period 1970–2005. Contrary to previous estimates, I find that the effective growth rate of well-being in the world, taking into account quantity and quality of life, was significantly below the growth rate of per-capita consumption.