title: How many people have lived on the earth?
abstract: A simple formula is proposed for estimating the number of people who have ever lived. Using assumptions that seem reasonable, an estimate of 69 billion (1960) is obtained. The present world population is about 4 percent of this number.
authors.affiliation: University of Chicago, Chicago, USA.
authors.forename: N
authors.initials: N
authors.lastname: Keyfitz