There are three types of countries in the world today as regards their population growth. Group A.-These countries have a very rapidly declining birth-rate, and although their death-rates are low their rates of natural increase are declining and they are rapidly approaching a stationary or decreasing population because of the general practice of conception control. Group B.-Birth-rates are coming under control in these countries, but rather slowly. Death-rates are declining more rapidly than birth-rates, however, so that natural increase is rising or at least is not declining to any great extent. Group C.-In these countries both birth-rates and death-rates are subject to little voluntary control as yet and the positive checks determine the growth of population. Land for expansion.-The land needed for the expansion of the peoples now entering upon a period of rapid population growth (practically all of those in Group B and some of those in Group C) is practically all being held by the peoples in Group A, who no longer have an expanding population to settle these lands. One of the most urgent problems of the next few decades is going to be the readjustment in land holdings demanded by this shift in the expanding peoples from northwestern Europe to eastern and southern Europe and to certain parts of Asia.