57 
attainable, human life being organised as at present, and 
even allowing that 31-2 per cent. is an underestimate. 
Continuing still the consideration on the lines 
indicated here, we note that we must, however, take 
account of the fact that of the 31-2 per cent. of the 
so-called productive land” only 32 per cent. is 
arable, hence the above estimated 17,642 millions of 
population is at once reduced to 5645, a figure almost 
identical with one of the results given in the end of 
the last chapter. Further, if it were supposed that the 
United States ratio of 503 to 800 could really be a 
possibility for the whole of this area, this would raise 
the limit only to about 8978 millions, an estimate 
of ultimate population that is very probably fairly 
accurate, the average standard-of-living remaining as 
it is at present. 
There is still another way by which we can get some 
idea of this earth’s ultimate population. Of the 52-5 
millions of square miles of land-surface some amount 
has to be deducted for rocky and mountainous regions, 
for deserts, and for cold and arid areas. All of these 
can never carry more than negligible numbers of 
human beings. Provision must be made also for 
necessary forests, and for animals both for food and 
clothing. Areas for cotton-growing, for sericulture, 
and for many minor purposes are -also required. When 
an allowance has been made for all of these, the area 
for agriculture which is to feed all will of course have 
been materially reduced. 
The aspect of the world’s possibilities which takes 
due account of the correlation of all human activities 
ought to be mentioned, for it very materially affects 
the possible numbers which the earth can carry, and 
affects also the rate at which those numbers can 
increase. For the social organism is so arranged that, 
to be most efficient, the numbers in industrial occupa- 
tions, those engaged in distribution, and those engaged 
POPULATION