There have been population movements like this in the past.
Many politicians are also keeping a close eye on population movement within the state.
There is strong evidence that despite population movement in the 19th Century most people stayed relatively near to their place of birth.
At the time, many people were concerned about the population movement away from farms and rural life.
As is presented above, however, there were no major population movements across the border.
But smaller populations are spread throughout the country, following recent population movements within Mexico.
This new knowledge may have come about by any combination of population movements and cultural contact.
This was done in response to the extensive and unexpected population movement from the country into cities.
The two most common theories are population movement and internal conflict.
On the most general level there would be a regulation of the international economy that includes population movements.