These conditions encourage and facilitate emigration and colonization, forms of historical movement which have characterized the great commercial peoples of antiquity and the overcrowded nations of modern times.

These forms do not involve a whole people, but only individuals and small groups, though in time the total result may represent a considerable proportion of the original population.

The United States in 1890 contained 980,938 immigrants from Canada and Newfoundland,[177] or just one-fifth the total population of the Dominion in that same year.

Germany since 1820 has contributed at least five million citizens to non-European lands.

Ireland since 1841 has seen nearly four millions of its inhabitants drawn off to other countries,[178] an amount only little less than its present population.
It is estimated that since 1851 emigration has carried off from County Clare and Kerry seventy-two per cent.