The exact number of people living on Earth at the present moment is (7,264,145,184). This is an estimate, and the historical figures are clearly even more speculative. The previous Probaway post, World population history graphed and smoothed, took several authorities’ estimates and drew a more easily remembered line through their speculations. Below I have tweaked those charts to make them even easier to memorize.
The intent of the World population history smoothed is to make more easily remembered the dates and their associated population numbers. That memorable line remains close to the estimates made by the authorities and well within the error bars marked in red lines. The Probaway estimate goes outside of the authorities’ own estimates for the year 1000 CE, but it is well within the error bars based on their data. The advantage gained by this method of presentation is easy memorization of some very complex data. The population of the world doubles each one thousand years for six thousand years. With that assumption the only fact that needs remembering is that at 1000 BCE there were 100 million people on Earth, and that the population doubled every thousand years.
The population since 1000 CE is different, but it too can be remembered easily within the error bars. The population in 1975=4 billion and doubles in fifty years both past and future. From 1925=2 billion to 1975=4 and will be 2025=8 billion. It had doubled in twice that time from 1825-1 billion, and doubled again in double the time from 1625-half billion. Learn these few facts and your estimate of the world population will be reasonably accurate for seven thousand years.