CERTAIN DEMOGRAPHIC BACKGROUNDS FOR POPULATION STUDIES 297 



our example the chances per 1000 of dying 

 within one year at age x. In certain ways 

 this is the most useful of the three graphs 

 since it depicts rates rather than absolute 

 numbers. The rate is high for infants, low 



for the middle period, and increases in 

 compound fashion as old age is attained. 



Nonhuman Populations. Life tables have 

 been worked out for a number of popula- 

 tions other than for man. Among these the 



10 20 30 40 50 60 70 80 90 100 

 AGE IN YEARS 

 Fig. 89. Survivorship (l^) curves for white males and females in continental United States, 



1929 to 1931. 







10 



20 



70 



80 



90 



30 40 50 60 



AGE IN YEARS 

 Fig. 90. Death curves (d^) for white males and females in continental United States, 



1929 to 1931. 



