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 Test Case by Steve Sailer on July 4, 2012.
• 700 Million Worldwide Desire to Migrate Permanently: U.S. tops desired destination countries by Neli Esipova and Julie Ray. The Gallup poll surveyed 259,942 adults in 135 countries from 2007 to 2009. The countries together house 93% of the world population.
• International Migration Desires Show Signs of Cooling: U.S. still top desired destination by Neli Esipova and Julie Ray, a follow-up that showed that by 2010, the number of peopledesiring to migrate had dropped to 630 million from the original 700 million in 2007.
• More Adults Would Move for Temporary Work Than Permanently: About 1.1 billion worldwide would move for temporary work by Julie Ray and Neli Esipova. The Gallup poll surveyed 141,000 adults in 119 countries between 2009 and 2010.
• Nearly 50 Million Worldwide Planning to Migrate Soon: Those working at capacity, professionals most likely prepping to leave by Neli Esipova and Julie Ray.
• Migration Could Triple Populations in Some Wealthy Nations: Some poor nations could see adult populations reduced by half by Neli Esipova and Julie Ray, reporting on the Gallup Potential Net Migration Index. A summary was written up by Filip Spagnoli here.

Open Borders blog post series related to migration count

• Migration: how many, what kind, and why it matters by Vipul Naik, July 23, 2013.
• A case for open borders that is radically agnostic about migrant count by Vipul Naik, July 31, 2013.
• Would migration levels under open borders be optimal, too high, or too low? by Vipul Naik, February 26, 2014.
• Factors constraining migration in the short run following significant migration liberalization by Vipul Naik, March 23, 2014.

Other speculative blog posts

• Response to Steve Sailer: The Art of Flourishing While Being Swamped by Nathan Smith on the Open Borders blog.
• Why open borders won’t work and Inconvenient questions about immigration by Tyler Cowen, where he argues that even though he is supportive of substantial increases in skilled and unskilled immigration, he does not favor open borders because it would undermine democracy and living standards of everybody, including the immigrants. Cowen further clarifies his position in The Open Borders attack.
• Questions on Immigration by David Henderson.
• Reply to David on Immigration by Bryan Caplan (reply to Henderson’s post linked above)
• Open Immigration: How Many Would Come? by David Henderson, containing further speculation on the question.
• What would happen if the United States lifted all of its immigration restrictions?: question on Quora, with multiple answers from different perspectives.