332 THE TREND OF THE RACE 
Considering the percentage of people living in towns of 2,500 
or more inhabitants, the urban population in the United States in 
1910 was 46.3 per cent and it is not improbably over 50 per cent 
at the present time. In several states over one-half the popula- 
tion lived in cities of 8,000 or more in 1910. It is evident that this 
country, despite its large size and the great extent of its agricul- 
tural industries, is fast following in the wake of the older nations 
of Europe in the urbanization of its population. In some parts, 
especially in New England, where the land has become partly 
exhausted or is relatively arid, the rural population in recent 
years has shown an actual falling off. 
The growth of cities is due to the following causes: (1) natural 
increase of their population, (2) migration, and (3) the incor- 
poration of outlying suburbs. These three factors vary enor- 
mously in different times and places. Gillette has attempted to 
estimate the relative share which each of these factors has played 
in the recent growth of cities in the United States. He separates 
the migrants into those from rural districts and those from foreign 
countries and presents the following table indicating the propor- 
tion derived from these different sources: 
Sources of Urban Growth in the United States 
Factor Number Per Cent 
Incorporation.................. 924,000 7.8 
Immigration sii.cces esse. vee ces 4,849,000 4I. 
Natural Increase................ 2,426,000 20.5 
Rural Migration................ 3,637,000 30.7 
Totaliisesey ini Sieg ese t03 11,826,000 100.0 
These figures cannot be more than a rough approximation to 
the truth owing to the lack of precise and extensive data on the 
movements of the population. It may be noted that natural 
increase is responsible for only a relatively small part of the urban 
growth in this country, and it is equally noteworthy that a 
