If the present trends in population continue, the United States is faced with a stationary or even a declining population in about 30 or 40 years. Similarly, the trend in number of families can be expected to follow this general pattern, although the pace may not be as rapid since the decline in size of family is an offsetting factor.

The figures presented above do not strictly represent the average size of private families in the United States, since they are obtained by dividing the number of private families in 1930 and the number of occupied dwelling units in 1940 into the total population for these years. The total population includes an appreciable number of persons who are not members of private families.

Estimated Population of the World by Continents.

Source: League of Nations Statistical Year Book, 1939-40; data are as of Dec. 31, 1938

(a) Excluding the U.S.R.R.: (b) in Europe and Asia; (c) including Mexico and Caribbean (40,870,000). These data contain estimates with a probably narrow margain of error: figures that are conjectural or uncertain--that is the census figures on the white population which is small in some countries and estimates as to the rest.