This smaller increase in the later decade is due partly to negro migration to the cities.

It is believed that among the city negroes, particularly in the North, the death rate is higher than the birth rate.

The excessive death rate results largely from crowded and unsanitary quarters.
Since 1910, the migration of negroes to the North has been larger than before.

The increase was not unusual, however, until the beginning of the Great War.

Up to that time the majority had been engaged in domestic and personal service, but with the practical cessation of immigration from Europe, a considerable number of negro laborers moved to the Northern States.