Flow Map

Flow maps use arrows to show size or direction of a variable. Flow maps can also be used to illustrate movement from one place to another. The flow map above show the " origins of asylum seekers" in the United States. The size of the arrows is a representation of the number of refugees. The arrows also show where the refugees were relocated. The map shows that a small number of South Americans traveled to Texas.

Source: http://www.cartisan.com/map_resources/map_types/flow_map.html