THE BIRTH-RATE 123 



numbers unaltered, about four children must be born 

 to each marriage that produces children at all. Of 

 these four, on the average of large numbers, two will 

 either die early or have no children, and the other two 

 will be left to continue the race in place of their 

 parents. Such is the result of the Registrar-General's 

 returns. 



We shall see later that certain large classes of the 

 people now produce an average of only three children 

 to each fertile marriage ; that is, only three-quarters of 

 the births necessary to maintain their numbers un- 

 altered. If their death-rate be taken at 15 in 1000, 

 their birth-rate must be about | of 15, or rather more 

 than 1 1 ; that is, about 4 less than the 1 5 needed to 

 replace the deaths. At the end of a year, there will be 

 about 996 instead of each 1000 persons alive at the 

 beginning of the year. At the end of a century — three 

 short human generations — each 1000 persons will be 

 represented by only 687, and in two hundred years by 

 472. 



The birth-rate of other sections of our people is still 

 some 23 P^J* 1000, or 13 more than are needed to 

 balance their higher death-rate of about 20. At the 

 end of one year, each 1000 will have become 1013 ; 

 at the end of a century, about 3600 ; and in two 

 hundred years, about 13,000. 



The less prolific stock, if originally equal in number 

 to the other, would be but about i in 6 at the end of 

 a century, while in two hundred years it would form 

 but about I in 30 of the population. It would be 

 lost in the descendants of the stocks of predominant 

 fertility. 



