THE NUMBERS OF MEN 



89 



human population. It is only an extrapolation from the available 

 evidence as to what the past history of world population growth 

 has been up to the present time. No other interpretation than 

 this should be put upon it. It is a figure that future events and 

 trends now wholly unpredictable may alter, just as proved to be 

 the case with the former extrapolation. 



z 



o 



3 

 Q. 

 Q_ 

 O 



a 



2300 

 2600 

 2-fOO 

 2200 



2000 



/soo 



/600 

 /400 

 /ZOO 



/doo 



300 

 600 

 •fQO 

 200 



/SSO 7S /70a 2S 50 7S ^00 2S SO 7S /SOO 25 JO 75 2000 25 SO 7S ^/OO 



YEARS 



Fig. 16. The population growth of the world from the seventeenth century to 

 1931-32. The circles give the observations, and the smooth line gives the graph 



of the logistic equation 



The present logistic cycle of world population growth got 

 discernibly under way at about the middle of the seventeenth 

 century — say three hundred years ago in round figures — and 

 started from a lower asymptotic value of about 445 millions. 

 This isj of course, only an estimate, but cannot be far away from 

 what was the actual fact. Indeed all competent students of 

 population agree on a value of about this general magnitude 

 for the time stated. Since then the world's population has in- 

 creased to about 2105 millions, again in round figures, as of an 

 average date of about 1935. In other words there has been in 



