THE CAUSES OF DEATH 113 



sex constitution of populations may make considerable 

 differences in crude death rates, in cases where no real 

 differences in the true force of mortality exist. What 

 is essential for the further prosecution of the analysis of 

 the causes of death is to get specific death rates for the 

 several causes. By an age and sex specific death rate 

 is meant the rate got by dividing the number of persons, 

 of particular specified age and sex, dying from a particu- 

 lar cause, by the total number of persons living in the 

 same population of the same age a/nd sex. In other 

 words, we need to get as the divisor of the rate fraction 

 the number of persons who can be regarded as truly ex- 

 posed to risk. This exposed-to-risk portion of the popu- 

 lation is never correctly stated in a crude death rate. 

 For example, a person now 75 years old cannot be re- 

 garded as exposed to risk of death at age 45. He was 

 once exposed to that risk but passed it safely. Yet in a 

 crude death rate he is counted with those of age 45. 



Age and sex specific death rates have hitherto been 

 available for the American people, in any general or com- 

 prehensive form, only from the extensive memoir by 

 DubUn, Kopf and Van Buren, based upon the mortality 

 experience of the Metropolitan Life Insurance Company 

 with its industrial poUoy holders. In a broad way, it 

 may be said that the data on which the following discus- 

 sion is based, derived fropi the general population of 

 the Eegistration Area, are essentially in accord with those 

 of Dublin on a more restricted group. Owing to limita^ 

 tions of space, it is not possible to present all the detailed 

 rates here. 



With the aid of Dr. William H. Davis, director of 

 vital statistics in the Census Bureau, who very kindly 

 provided me with the necessary unpublished data, it has 



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