Opening up borders and encouraging geographic mobility for migrant workers is often a point of controversy. Critics claim that these lower-paid workers effectively steal jobs from exiting citizens and can lead, in extreme cases, to the overpopulation of certain areas, putting a strain on public services and pushing up the local cost of living. This can then fuel hatred and spur social unrest. Economists, on the other hand, often argue that migrant workers take low-paying, low-skilled work that nobody else wants or whom would require higher wages. A growing population also usually corresponds with economic growth and prosperity.