See also: precautionary principle and moderate versus radical open borders.

In the vein of the precautionary principle, one of the concerns that some people have with open borders is that the developed world would get swamped with large numbers of people from developing countries. This is a serious and important concern, although it does not really apply to moderate increases in immigration.

See also moderate versus radical open borders.

To quantify this worry, one would need to consider the hypothetical: what would happen under an open borders regime?

The concept of diaspora dynamics, popularized by Paul Collier, where migration levels are initially small and gradually grow as existing diasporas attract more migrants, is helpful in understanding the issue.

Polling data

For more polling data, see polling data on migration and Gallup surveys on migration.

The relevant polls are included below:

Open Borders blog post series related to migration count

Other speculative blog posts

"The Efficient, Egalitarian, Libertarian, Utilitarian Way to Double World GDP" — Bryan Caplan