@article{Cohen_S8_56,
author = {Cohen, Joel E.},
title={{Is the fraction of people ever born who are currently alive rising or falling?}},
journal = {Demographic Research},
volume = {S8},
number = {56},
pages = {1561--1570},
doi = {10.4054/DemRes.2014.30.56},
year = {2014},
abstract = {Background: Some journalists and demographers have asked: How many people have ever been born? What is the fraction F(t) of those ever born up to calendar year t who are alive at t? The conditions under which F(t) rises or falls appear never to have been analyzed. 

Objective: We determine under what conditions F(t) rises or falls. 

Methods: We analyze this question in the model-free context of current vital statistics and demographic estimates and in the context of several demographic models. 

Results: At present F(t) is very probably increasing. Stationary, declining, and exponentially growing population models are incapable of increasing F(t), but a doomsday model and a super-exponential model generate both increasing and decreasing F(t). 

Conclusions: If the world's human population reaches stationarity or declines, as many people expect within a century, the presently rising fraction of people ever born who are now alive will begin to fall. 

Comments: It is curious that nearly all empirical estimates of the number of people ever born assume exponential population growth, which cannot explain increasing F(t). },
URL = {https://www.demographic-research.org/special/8/56/},
eprint = {https://www.demographic-research.org/special/8/56/s8-56.pdf}
}