THE MIGRATION OF POPULATIONS 73
that naturally occurs is, “ How quickly can the world
advance to such densities as have been referred to, for
her peoples?” and the second is, “In what regions
will the situation first become one of challenging
difficulty? 2” We may, therefore, perhaps at the risk
of being tedious, refer again to the significance of the
rates of growth. For the last one hundred years it
may be taken as two-thirds of a per cent. per annum.
Assuming the world-population for 1928 to be 1950
millions, the four limits 5200, 7020, 9ooo and
11,000 would be reached in only 1476, 1928, 230-2
and 260-4 years respectively, if the rate continued
constant; that is, before the following years of this
era, viz., before the year 2076, or 2121, or 2I§8,
or, finally, before 2188. These are but short periods
in history; they are very roughly only about one-
thirteenth, one-tenth, one-eighth, and one-seventh
respectively of the present era of 1928 years.
If the annual rate for the western world from 1906
to 1911, viz., 116 per cent. per annum, were to hold
continuously for the whole world, these limits would
be reached in much less time, viz., in 85-0, 111-1,
1326 and 150-0 years respectively. It does not
materially alleviate the situation, either, to be told
that the rates of increase will diminish as the limit,
whatever it be, is approached, and that the ultimate
figure will be very slowly reached. Long before
that figure has been attained the population-difficulty
will have become terribly acute, and it has to be
borne in mind that, from time to time, the trouble
about populations and their food-supplies is certain
to be painfully accentuated by the inescapable vicissi-
tudes of Nature. Man can cope with these to some
extent, it is true, but, after all, only very inefficiently.
He has learnt to modify the disaster coming upon
him through a drought, but he cannot wholly escape
appalling losses. Recently he has again been reminded