244 



BIOLOGY OF DEATH 



by virtue of a supposed general positive correlation be- 

 tween birth-rates and death-rates. 



The relation of birth-rate and death-rate changes to 

 population changes is a simple one an.d may be put this 

 way. If, neglecting migration as we are justified in 

 doing in the war period and in considering the world prob- 

 lem, in a given time unit the percentage 



100 Deaths 



Births 



has a value less than 100, it means that the births exceed 

 the deaths aud that the population is increasing within 

 the specified time unit. If, on the other hand, the per- 

 centage is greater than 100, it means that the deaths are 

 more frequent than the births and that the population 

 is decreasing, again within the specified time unit. The 



TABLE 29 

 Percentage of Deaths to Births 



* First three-fourths of year only. 



ratio of deaths to births may be conveniently designated 

 as the vital index of a population. 



From the raw data of births and deaths, I have cal- 

 culated the percentage which the deaths were of the births 

 for (a) the 77 non-invaded departments of France; (b) 



