CERTAIN DEMOGRAPHIC BACKGROUNDS FOR POPULATION STUDIES 291 



point we have assembled crude death rates 

 for the United States, England and Wales, 

 Sweden, and Italy, extending for the last 

 four countries from 1871 to 1938 and for 

 the former from 1901 to 1940. These rates 

 are graphed in Figure 87. 



Probably the most important point in 

 Figure 87 is the downward trend of the 

 death rate for all four countries over the 

 sixty-odd years of observation. During this 

 interval the curve of ecological mortality 

 steadily approaches (with the exception of 

 the war years) the curve of physiological 



matters pertaining to health and group 

 living. 



Figure 87 also allows some instructive 

 comparisons between countries. It is patent 

 that Italy is in a "curve family" by itself. 

 There is no confluence between its line and 

 those of the other three. Also, it is true that 

 Italy started to control its excessive mortal- 

 ity about 1920; from that time on the 

 trend is consistently downward. In the last 

 quartile of the nineteenth century Sweden 

 had a distinctly lower death rate than did 

 England and Wales. This persisted until 





YEAR 



Fig. 87. Deaths per 1000 for Sweden, England and Wales, Italy, and the United States. 



(From Lotka. ) 



longevity. Italy, starting with a rate of 

 thirty deaths per 1000 population in the 

 1871 to 1880 interval, in 1938 had a rate 

 of 13.9— a decrease of about 53 per cent. 

 Sweden drops from 18.3 to 11.5, a 37 per 

 cent decrease. The trends for England and 

 Wales and the United States are essentially 

 similar to those of Sweden as well as to each 

 other. There is no doubt that the decline in 

 mortaUty is real, although the causal factors 

 are somewhat more obscure. As a general 

 assumption, it seems safe to conclude that 

 the major cause is not a genetic difference 

 between the organisms of 1870 and those 

 of 1940, but, rather, a fundamental better- 

 ment of the population ecology. Probably 

 the most important factor-complex is an 

 improvement in the practices of pubhc 

 health and preventive medicine along with 

 a gradual education of the populace about 



about 1910, when the two became reason- 

 ably similar. The United States also falls 

 into this pattern. 



The final point of interest is the striking 

 relation between World War I and the 

 dealh rate. This holds true for all countries 

 whether belHgerent or nonbeUigerent. Italy's 

 rate jumped from 19.2 in 1917 to 32.9 in 

 1918; Sweden's from 13.4 to 18.0; and the 

 United States' from 14.3 to 18.1. England 

 and Wales had two accelerations: one in 

 1916, when the rate went from 14.0 

 (1915) to 15.7, and the other in 1919, 

 when it increased from the 1918 figure of 

 14.3 to 17.3. Again the interpretations are 

 difficult, although the influenza pandemic 

 and a general worsening of hving standards 

 consequent on the war come to mind as 

 significant contributing causes. It is inter- 

 esting to note that Italy, with a past history 



