How Many Old People Have Ever Lived on Earth?

Dalkhat M. Ediev, Wittgenstein Centre (IIASA, VID/ÖAW, WU)
Gustav Feichtinger, Wittgenstein Centre (IIASA, VID/ÖAW, WU) and Vienna Institute of Demography
Alexia Fürnkranz-Prskawetz, Vienna University of Technology
Miguel Sanchez Romero, Vienna Institute of Demography and Austrian Academy of Sciences

Recently, Cohen (2014) revisited the popular question some demographers have asked: How many people have ever been born? In particular he studies the fraction of those ever born up to a calendar year T, who are alive at time T, for age y = 0. The present paper extends this methodology to the proportion of people, who have ever reached a certain age y, say 65 years, and are alive today. In this paper, we first analyze this fraction by using demographic data based on UN estimates. Opposite to the claim made by Fred Pearce (The Economist, 2014): “it is possible that half of all the humans who have ever been over 65 are alive today”, we estimate that the proportion (at y=65) is much smaller, ranging between 5.5 and 9.5%. Moreover, we show the main properties of the proportion by age and over time.