356 



HUMAN BIOLOGY 



occupations. Particular death rates for the principal causes 

 are with few exceptions higher for urban than for rural 

 populations (Table i). 



THE EXPECTATION OF LIFE 



More satisfying than death rates in picturing the relative 

 healthfulness of groups of people is the Hfe expectancy table 

 in which we see reflected the experience of the past in terms 

 of probabihty of survival of those now living. It may be 

 explained that the "expectation of hfe" is the average length 

 of life remaining to all persons alive at the beginning of a 

 specified year of age. For our present purpose we can quote 

 as applicable, with a high degree of probability, the experience 

 of the white race in the original registration states (New 

 England, New York, New Jersey, Indiana, Michigan and 

 District of Columbia). The rural population described is that 

 part of the people living in communities of 10,000 or less. 



Table hi 

 expectation of life for the white population of the original 



REGISTRATION STATES (iQOp, IQIO, Ipll) 



(Bureau of the Census, U. S. Life Tables, 1910) 



There Is then no exception to the advantage at every 

 age group of the rural as compared with the city dweller 

 in the average length or expectancy of life. 



This does not, however, tell the whole story any more 

 than one can get all the truth from the death rates of an 

 individual year. These figures mean that under a uniform 

 condition as to death rates at each age group, equal to that 

 of the period 1909-1911, a male child born and continuing 



