Posted on May 10, 2019

How Many Would Really Come if the Borders Were Open?

Matthew Sussis, Center for Immigration Studies, May 8, 2019

A recent global Gallup poll found that 158 million adults around the world said they would migrate to the United States if they could. However, Gallup only polled adults, meaning the actual total number of people who would come to the United States is much larger because it would likely include children. {snip}


Of course, as Gallup notes, the number of actual migrants tends to be much smaller than the number of potential migrants. Still, these eye-opening numbers highlight the risks of an open-borders scenario, where anyone who’d like to come to the United States with their family has that option.

Scenario 1: Regional Fertility Rates

In our first scenario, we consider the fact that Gallup does not clarify which countries these 158 million adults come from, but it does tell us the total proportion of adults seeking to move to anywhere — not the United States specifically — by region. For example, 33 percent of Sub-Saharan African adults say they would leave Sub-Saharan Africa if they could; 27 percent of Latin American and Caribbean adults feel the same way.

As such, certain regions — Africa, Latin America, and the Middle East — are heavily overrepresented among potential migrants. {snip} Sub-Saharan Africans account for 14 percent of the global population, but 29 percent of total potential migrants.

By applying those proportions to the 158 million adults who want to move to the United States, we can estimate the total number of potential migrants by region. For example, in this scenario we estimate that 23 million of those 158 million people would come from Latin America.

However, with regard to children, different parts of the world have different family sizes and different total fertility rates (i.e., the number of children likely to be born to a woman from that country over the course of her child-bearing years at current birth rates). {snip} Scenario 1 uses regional fertility rates to estimate the ratio of children to adults for each adult migrant coming to the United States.


Under this scenario, we estimate that 158 million adults moving to the United States would bring 227.6 million children with them, for a total migration wave of 385.6 million people.

Scenario 2: Chain Migration Multiplier


In a hypothetical scenario where 158 million adults move to the United States in a short period of time, it’s quite likely that the multiplier would rise even more, given that people are more likely to immigrate if they know someone else who has immigrated, and given that the multiplier has risen over time.


Given these confounding variables in both directions, it seems most fair to simply apply the existing 3.45 multiplier to the 158 million people. Doing so would lead to an additional 545.1 million migrants, for a total migration of 703.1 million people.