World Population Data
According to
UNITED NATIONS DESA / POPULATION DIVISION
World Population Prospects 2017
Item Medium Estimate High Estimate Low Estimate
World Population Count:      
World Population Growth Tempo:
 

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Global Birth Tempo:
 

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Global Death Tempo:
 

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An interesting derivation:
Note: billion = 1 000 000 000 = milliard or so in many other languages.
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World Population: P = billion
Maximum possible number of
monogamous couples (all ages):
C = P/2 = billion
ESTIMATED number of regularly sexually
active couples (initial estimate = C/2):
N: billion
ESTIMATED average duration
of such an activity:
D: minutes
ESTIMATED average frequency
of such activities:
F: per week
Total world-wide activity frequency: K = N×F = per week
Duration of a week: W = 7×24×60 = minutes
Average fraction of time
couples are active:
A = D×F/W = 1 :
Ergodic hypothesis: If each couple is active for 1 : of the time,
then 1 : of all couples are active at any moment.
So, if N, D, and F are accurate estimates: N×A = couples world-wide
are having sexual intercourse
World-wide births per week: BW = per week = per minute
Births per activity: S = BW/K = 1 :
Average female reproductive period:
R: years
RW = R×(365.25/7) = weeks
Number of activities in that time: Y = RW×F =
Average total births per active woman: Z = Y×S =
Note: C = P/2 = NW = total number of women and N = no. of active couples = no. of active women.
Defining: AF = N/NW = active fraction of women, so N = AF×NW,
and: RF = RW/LE = reproductive fraction of life time, so RW = RF×LE
(LE = female Life Expectancy, U.N. medium estimate for 2015-2020 = 74.29 years = 3876 weeks)
yields: Z = BW×RW/N = BW×(RF×LE)/(AF×NW) = BW×(RF/AF)×(LE/NW).
RF is the reproductive fraction of a life time, AF is the sexually active fraction of the population.
Ergodicity would mean RF = AF and the above initial values of N and R more or less reflect that.
It makes Z = BW×LE/NW.
Since BW×LE is the total number of births during a period of the same length as an average female life time,
this fertility number simply equals the number of births divided by the number of women.
Compare the above value of Z to the official U.N. values
taken from this Excel file.
1950-1955: 4.961955-1960: 4.891960-1965: 5.031965-1970: 4.921970-1975: 4.46
1975-1980: 3.871980-1985: 3.601985-1990: 3.441990-1995: 3.021995-2000: 2.75
2000-2005: 2.632005-2010: 2.572010-2015: 2.52  
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Info
As far as I can find out, data given by Worldometers are mainly based on U.N. data, but Worldometers currently shows a lower number than the page you are reading right now. This page uses data directly extracted from Excel sheets downloaded from the U.N. website. As you can see above, the "official" milestone dates given by the U.N. are largely inconsistant with their own detailed data. A probable cause is that accurate details became only available a few years after the milestone was proclaimed.
You can view the source code of this page (right-click on a non-active area of the page and find your way in the context menu), and especially its accompanying JavaScript file. The latter contains all URLs I used.
This page uses Linear Interpolation between data points (as well as linear extrapolation beyond 2100 for those who like to read tea-leaves).
I did not use any data from the U.S. Census Bureau, which presents lower numbers than the U.N. and Worldometers. It is up to you to consider it either optimistic or pessimistic...
Primary data source: https://esa.un.org/unpd/wpp/
secondary data source: http://www.worldometers.info/
Copyright © 2017 Henk-Reints.nl
Page last updated: 2017-08-19.