626 PROCEEDINGS OP SECTION G. 



6. INVESTIGATIONS CONCERNING A LAW OF 

 INFANTILE MORTALITY. 



By Chas. H. Wickens, A. I. A., Commonwealth Bureau of 

 Census Statistics. 

 1. Mortality Amongst Infants Under One Year of Aoe. 

 In many statistical publications the expression " infantile mor- 

 tality " is used in connexion only witli the deaths of children 

 under one year of age. In such cases it is usual to deduce the rate 

 of infantile mortality by dividing tiie total number of deaths under 

 one year of age recorded in any calendar year by the number of 

 births recorded in the same year, and to express the quotient 

 obtained as a ratio to 1,000. For general purposes it is probable that 

 the result so obtained gives the infantile mortality rate v^'ith a 

 fair degree of approximation, although in strictness it must be 

 admitted that two vitiating circumstances are in evidence, viz., 

 (i) the fact that the deaths under one year of age occurring in any 

 calendar year are drawn largely from the cliildren born in the pre- 

 ceding calendar year, and (ii) the fact that neither birth nor death 

 registrations for any calendar year represent exactly the occur- 

 rences for that year. 



If the number of births remained fairly constant froin year to 

 year, no appreciable error would be introduced. If this number it 

 not sensibly constant, it would be desirable to make some allow- 

 ance for the overlapping. For this purpose, the mean of the num- 

 ber of births for the year of observation and the number for the 

 } receding year has been employed in the present paper, in place of 

 the number for the year of observation only. 



2. Infantile Mortality to Age 5. 

 For many purposes the view preseuted by taking account only 

 of the first year of life is incomplete and may be misleading. A 

 moderately heavy death rate at age may be succeeded by a re- 

 latively light rate at ages 1, 2, 3 and 4; while, on the other hand, 

 a fairly light rate at age may be succeeded by relatively heavy 

 rates at the higher ages. It appears desirable, therefore, in investi- 

 gations concerning infantile mortality to obtain results at least as 

 far as age 5. In the present paper the results for the Common- 

 wealth of Australia for the decennium 1901-10, as far as age 6 

 are given in some detail as an example of the method employed, 

 and it is shown that a mathematical expression of the Makeham- 

 Gompertz type may be used to obtain a representation of the rates 

 of mortality for the first five years of age. 



3. Infantile Deaths During the Decennium 1901-1910. 

 During the decennium 1901-10 the total number of deaths re- 

 corded in the Commonwealth of children under the age of 5 yean 



