CHAPTER V
HOW POPULATION INCREASES
THE question how any particular population increases,
and why its rate of increase may change at different
stages of its development, is not only interesting per se,
it is, as we have seen, a question of great practical
importance, and is specially so whenever an attempt
is made to forecast its future growth. It may be
mentioned that, between 1909 and 1923, the world
was increasing at a rate which would double its popu-
lation in 104-32 years, or say in round numbers 10§
years. This may be taken as one of the most recent
fairly accurate estimations covering a sufficient period
to give results of value.
Accepting this, and assuming—to suppose the
impossible—that this rate of increase is to go on
unchanged, it is instructive to inquire what the effect
would be as regards the total population at different
dates, how many persons this would give to the square
mile, and further what area, on the average, each would
occupy. The answers to these queries enables us
better to envisage the significance of the numbers. In
the table below the date-years are Iog apart, the
population being always doubled. The second line
gives their numbers in millions. The third is the
number per square mile. The fourth gives the side of
a square, which each would occupy if they could be
distributed uniformly over the 52-5 millions of square
miles of land-surface. The fifth line gives the name
of the country whose average density of population
most nearly agrees with that shown on line three,
Bl