At the beginning of the present century, therefore, there were only 8 States in which the population was more than one-half urban. In 1910, New Hampshire, Ohio, Maryland, Colorado and Washington were added to the list; in 1920, Indiana, Michigan and Delaware; and in 1930, Wisconsin, Missouri, Utah, Florida and Oregon.
Table IV shows the population in 1910, 1920 and 1930, of those cities in the United States which had 300,00o inhabitants or more.
The corresponding figures for the main elements of the population were as follows: for native whites, 50.3 and 49.7; foreign-born whites, 53.5 and 46.5 ; Negroes 49.2 and 5o.8. In the proportions of the sexes in the aggregate population there has been almost no change since 1820. In the immigration since the restrictions of 1924 there has been an increasing proportion of women which presumably indicates a more stable class of immigrants. In densely settled regions females are proportionally more numerous as a general rule. In Massachusetts, Rhode Island, Connecticut and the Southern States of North Carolina, South Carolina, Georgia and Alabama there are more females than males. In the more thinly settled Western States males predominate, there being in the Mountain States 111.3 males, in the Pacific States 108.7 males for every ioo females. In 1920 there were among every 1,000 urban inhabitants 18 (in 1900, 24) more females than among 1,000 rural inhabitants. In 1930 there were 98.1 males per ioo females in the urban population. In the whole United States the number of males per 1 oo females in 1930 was 102.5, as compared with 104.0 in 1920 and 103.3 in 1820, the highest ratio in any intervening year being 106.0 in 1910.
Age.-The median age of the population of the United States -that is, the age which divides the population into two equal groups, one younger and the other older-has shown an increase each decade from 180o, when it was 15-97 years, to 1930 when it was 26.4 years, the median ages for 1910 and 1920 being 24.0 and 25.2 years, respectively. The increase has been due chiefly to two causes: first, an increase in the average length of life; second, a reduction in the birth-rate, which results in a decrease of the proportion of young persons in the population. Also an increase in immigration tended to raise the median age since most immi grants come as mature persons. The median age of the foreign born white in 1930 was 43.9. The median age of native whites was 23.7 ; of Negroes, 23.4; and of American Indians, 19.6.
Vital Statistics.-Statistics of births and deaths have been collected annually from all of the States in the United States since 1933. Prior to that date they were collected from a gradu ally increasing registration area, made up of all those States wherein at least 9o% of the births or deaths were believed to be reported.
The death rate, that is, the number of deaths per i,000 of the population, in the registration area was 17.6 in 'goo; 15.o in Iwo; 13.6 in 1915; 13.0 in 1920; 11.8 in 1925; 11.3 in 1930; 11.2 in 1937; and 10.6 in 1938. There was considerable variation in the death rate between 1915 and 1920, the rate rising as high as 18.1 in 1918 by reason of war casualties and the even more disas trous epidemic of influenza in that year. The death rate in the United States in 1937 was lower than in any other important na tion except Australia and New Zealand, though the rates for Eng land, Wales, Sweden and Germany were but slightly higher.
In 1937 there were 1,450,427 deaths, of which 346,401 were from diseases of the heart; 144,774 were from cancers and other malignant tumours; '10,009 were from pneumonia; 102,877 were from nephritis; 99,577 were from cerebral haemorrhage and sof tening; 69,324 were from tuberculosis; 63,349 were from con genital malformations and diseases of early infancy; 39,643 were from motor vehicle accidents; and 38,005 were from influenza.