With European colonization and migration, positive aspects of European culture spread across the globe in spite of obstacles.

In the process known as step migration, migrants move from rural to urban areas through a series of smaller moves, or steps.

Each migration produces a counter migration of people returning to their country of origin.

The gravity model predicts that most migrants will move to the closest large metropolitan area in search of economic opportunities.

Migrants leave their homelands because of push factors and move to places with pull factors, but they often face barriers as they migrate.

High unemployment countries in Stage 4 and 5 of the DTM pushes migrants to Stage 2 and 3 countries in search of economic opportunity.

Overcrowding in countries in Stage 2 and 3 of the DTM pushes migrants to Stage 4 and 5 countries in search of economic opportunity.

Overcrowding in countries in Stage 4 and 5 of the DTM pushes migrants to Stage 2 and 3 countries in search of economic opportunity.

A gender imbalance in countries in Stages 4 and 5 of the DTM pushes migrants to Stage 2 and 3 countries to find mates and start families.

Overcrowding in countries in Stage 4 and 5 of the DTM pushes migrants to Stage 2 countries in a counter migration as large as the original migration.

Between 1830 and 1930 most U.S. immigrants were slaves; between 1930 and the present most were free persons.

Between 1830 and 1930 most U.S. immigrants were wealthy; between 1930 and the present most were poor.

Between 1830 and 1930 most U.S. immigrants were English speakers; between 1930 and the present most immigrants were non-English speakers.

Between 1830 and 1930 most U.S. immigrants were from the Americas and Asia; between 1930 and the present most were from Europe.

Between 1830 and 1930 most U.S. immigrants were Europeans; between 1930 and the present most were from the Americas and Asia.