NATURAL DEATH, PUBLIC HEALTH 249 



This theory* of population growth makes it possible 

 to predict what the maximum population in a given area 

 will be, and when it will be attained. Furthermore, one 

 can tell exactly when the population is growing at the 

 maximum rate. To test the theory, we have only to fit 



Fio. 60. Showing a theoretical curve of population growth. 



this theoretical curve to the known facts of population 

 for any country by appropriate mathematical methods. 

 If the hypothesis fits well all the known facts for a variety 

 of countries in different stages of population growth, it 

 may well be regarded as a first approximation to a sub- 

 stantially correct hypothesis and expressive of the bio- 

 logical law according to which population grows. In 

 making this test the statistician has somewhat the same 



* The mathematical hypothesis here dealt with is essentially the same 

 as that of Verhulst, put forth in 1844. As Pearl and Reed pointed out 

 in their first paper on the subject it is a special case of a much more 

 general law. A comprehensive general treatment of the problem we are 

 publishing shortly in another place. The generalization in no way alters 

 the conclusions drawn here from a few illustrative examples. 



