POPULAR ERRORS REGARDING THE 

 DURATION OF LIFE. 



A paper read before the Essex Institute, Oct. 9, 1882. 



BY ADONIRAM C. ORNE. 



THERE is probably no subject on which so much has 

 been written, so much labor bestowed, which is so little 

 understood as the duration of life. The popular idea is 

 that a generation passes away in about thirty-three years. 



I shall endeavor to show that this is a very great mis- 

 take and arises from a misapprehension pf the facts in the 

 case. I propose to show that we live much longer, and to 

 point out where statisticians make their mistakes. 



It is universally admitted that not exceeding two per % 

 cent of the entire population die annually. This fact 

 being admitted, it follows logically that, if two per cent 

 die in one year, it will require fifty years for the whole 

 population to die ; and if it requires fifty years for a 

 generation to pass away, this establishes the fact that the 

 average life of a generation is fifty years instead of thirty- 

 three as is generally supposed. 



The mistake arises from the fact that in making up 

 their calculations statisticians do not take into considera- 

 tion the difference between the average age at death and the 

 average duration of life. For example, suppose you 

 want to get the duration of life of oiie thousand children, 

 you must first ascertain the age at death of the entire 

 thousand which cannot be done until all have" passed 

 away. 



The mistake arises with our statisticians from the fact 

 that they attempt to give it before half have died. They 

 base their calculations upon the number of deaths without 

 taking into consideration the increase of population aris- 



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