292 



POPULATIONS 



of high mortaUty and poor sanitation, had 

 a greater actual and relative rise during the 

 war years than the other countries. 



Specific Death Rates 



In its various fonns the specific death 

 rate is a widely used and useful statistic. 

 It is commonly apphed to age, sex, race, 

 occupation, location of dwelHng, and as a 



statistic (Fig. 88). We see that all fou; 

 curves (1910 males, females; 1930 males 

 females) have a characteristic form. There 

 is a high death rate under one year of age 

 representing the infant mortality compo 

 nent; a low death rate between nine years 

 and, say, thirty to forty years, followed 

 thereafter by a rapid increase through mid- 

 dle and old age. 



^500 



05 



X300 



UJ 



(/) 



X 200 



O 



< 



UJ 



u. 



O 100 



Z 70 

 > 



-• 50 

 O 



o 



^ 30 



q: 



y 20 



(/) 



UJ 



en 



< 10 



< 



_ 5 



< 



or 



X 

 UJ 



o 



TOO 



20 



40 60 80 100 



AGE IN YEARS 



20 40 60 80 



AGE IN YEARS 



Fig. 88. Age and sex-specific death rates for 1910 and 1930, United States census data. (From 



Pearl. ) 



measure of infant mortaUty. The definition 

 is 



where Rg is the specific death rate; Dg, the 

 deaths in a specific class of the population; 

 and E, the number exposed to risk of dying 

 in the same specified class of the population 

 from which the deaths came. These rates 

 are usually stated "per 1000." 



A case computed by Pearl (1940) on 

 age and sex-specific death rates for twenty 

 states of the United States population in 

 the years 1910 and 1930 will illustrate this 



In terms of sexual differences the females 

 as infants may have a higher mortality than 

 do the males, but if they live to be one year 

 old their prospects for long hfe in the statis- 

 tical sense are better. Insofar as informa- 

 tion is available, this sex differential apphes 

 generally to most animals; it is not hmited 

 to man (see discussion under the Life- 

 Table, p. 294). 



The final point to be made from Figure 

 88 is that in the twenty years between 

 1910 and 1930 the mortality decreased for 

 all sexes and for all ages. The greatest re- 

 ductions occurred from birth through age 

 fifty. There is some, although relatively 

 slight, difference during later life. 



