472 



Prof. K. Pearson. 



[June 4, 



country and considerable periods are dealt with. I think we may say with 

 fair certitude, for example, that of 1000 male children bom in the period 

 1871-1880, 158 - 58 would die in the first year of life, and of their survivors, 

 841 in number, (841/1000) x 127-58 would die in the second to the fifth years 

 of life. Further it must be remembered that owing to the period (10 and 

 16 years) covered, the arrays born in each year but the last one or two 

 have contributed their survivors to die in the whole or part of the child 

 period 1 — 5. 



My next point is the problem of environment. We are told that the 

 environment has been continuously improving during the last 40 to 50 years, 

 and if we ask for a measure of it we are very rightly referred to the falling 

 death-rate, which remained stationary until 1866, and then has been falling in 

 a remarkable way ever since. To correct therefore for continuously improving 

 environment we may take something closely associated with the death-rate ; 

 it occurred to me that expectation of life would be an excellent measure of 

 this change of environment. In order, however, to introduce no spurious 

 correlation by taking the expectation of life at birth, which would include the 

 influence of the very mortalities I am dealing with, I have taken the 

 expectation of life at the age of 6 years as the factor by which to correct for 

 the secular change in environment.* 



Of course, I very fully realise the audacity of determining correlations 

 from four life-tables only,f but it must be remembered that each one of my 

 figures is based upon a population of millions, and even if we considered our 

 total number of observations four only, the fundamental partial correlations 

 are still immensely significant as compared with their probable errors. 

 Further, I shall show that calculated and observed results are in agreement. 



Tables I and II give the data. Underneath the tables I have placed the 

 chief statistical constants ; i = infantile death-rate (0 — 1 years) in deaths per 

 thousand ; c = death-rate of children (1 — 5 years) in deaths per thousand ; 

 e = expectation of life in children aged 6. 



* Should it be said that the expectation of life at six years of age is influenced by the 

 mortality which occurs in the first five years, this in itself would be to admit that the 

 death-rate is truly selective, the very point we have set out to prove, as against those 

 who hold that the infantile death-rate is not selective. 



t We have to bear in mind the vast amount of work involved in computing a table of 

 this kind, and recognise that in calculating 14 life-tables in four series the General 

 Registry Office has achieved a great task. 



