March 16 was “Open Borders Day.” I’m celebrating a day late. Here is a relevant excerpt from Libertarianism: What Everyone Needs to Know.

Libertarians…advocate open borders and free immigration. Libertarians advocate free immigration in part because immigration restrictions are highly inefficient. When economists try to measure the deadweight loss immigration restrictions cause, they typically estimate that eliminating all immigration restrictions would double world GDP. That is, we could add another $70 trillion to the world economy in a few years if only we liberalized immigration laws.

A good way to think about this: If you oppose open borders, do a cost-benefit analysis. You need the expected costs to be around 70 trillion dollars. Otherwise, your CBA comes out in favor of something like open borders.

But let’s put CBA aside. There’s a strong prima facie deontological justification for open borders:

Libertarians…believe that immigration restrictions are pernicious. Libertarians believe immigration restrictions impose poverty, suffering, pain, and death on some of the most vulnerable people in the world. Philosopher Michael Huemer explains this with a thought experiment: Imagine starving Marvin heads to the market looking for food. Marvin has little to trade. However, suppose there are people at the market willing to trade food for whatever Marvin has. Imagine that unless someone stops him, Marvin will successfully get to the market, make the trade, and eat. However, now imagine that you forcibly prevent Marvin from getting to the market. You post guards to keep him out. The guards continually capture Marvin and turn him away. Marvin can’t barter for food. He starves and dies. In this situation, Huemer says, you have done something morally comparable to killing Marvin. His blood is on your hands. In another version of the story, imagine Marvin is not starving, but is instead desperately poor. Imagine that if Marvin makes it to the market, he will make some trades and instantly become ten times richer. Imagine Marvin will be able to send large amounts of money back to his poor village to feed his entire extended family. However, again, you post guards, who turn Marvin away. In this case, you force Marvin to stay poor. It was not your fault Marvin was poor to begin with, but it is your fault he remains poor. Huemer admonishes us: In these thought experiments, you do not simply fail to help Marvin. That is, you are not doing something equivalent to walking by a beggar without donating spare change. Instead, you actively hurt Marvin by using violence to prevent him from making a trade with a willing partner. It is as if you saw someone else offering a beggar $5 to wash a car window, but you scared the beggar and the driver away with your gun. Libertarians believe immigration restrictions are morally equivalent to keeping Marvin from the market in the thought experiments above. Some people in rich countries want to hire poor foreigners. The foreigners want the jobs. These jobs make the difference between life and death or prosperity and poverty. Immigrants to the United States usually see their income rise by an order of magnitude or more—they go from desperately poor to relatively wealthy almost overnight. But the United States and other countries post armed sentries around their markets. They use violence to stop foreigners from making life-saving or life-changing trades with willing partners. This is morally equivalent to killing the foreigners or forcing them to stay poor.

If you aren’t in favor of open borders, it’s not clear you get to count as an advocate of social justice:

Many on the left in American and European politics claim to care about the poor. But their hearts bleed for the American and European lower classes—that is, for people who are wealthy by world standards—not for the world’s poorest people. Most people on the progressive left actively try to restrain the world’s poorest and most vulnerable people from making life-saving and life-changing trades with willing employers. They thus condemn the world’s poor to death and misery. The progressive left is delighted with me when I donate money to the poor through OxFam. But the Left forbids me from hiring the poor to mow my lawn, even though that helps them more than an OxFam donation. From the libertarian point of view, if you do not advocate open immigration, any claim to be concerned about social justice or the well being of the poor is mere pretense.

Strong words, but I mean it. I regard Rawls as a conservative critic of social justice.

How this relates to the sweatshop debate:

Libertarians add: next time you see a person protesting sweatshops, ask the protestor what she thinks about immigration. She probably opposes allowing poor and unskilled immigrants to travel freely in search of work. But when we have an economic system in which everything—financial instruments, money, factories, services—can be globalized and move freely across borders, except poor, unskilled labor, what happens to the poor people who supply unskilled labor? They will not be able to travel in search of opportunities. They will instead be forced to sit and wait for opportunity to find them. It is thus no surprise that the only opportunities that find them involve low wages and sweaty conditions. In short, our immigration laws make the most vulnerable members of the world sitting ducks for exploitation.

What are the objections to open borders?

Those who defend immigration restrictions might agree that such restrictions appear evil at first glance. However, they argue, the restrictions can be justified. They argue that Free immigration would disrupt and destroy native culture. Free immigration reduces the wages of native-born workers. Free immigration would cause high crime. Immigrants will consume too many welfare services. Libertarians say that even if the first worry were true, it is not a strong enough concern to justify condemning the world’s poor to poverty, suffering, and death. Perhaps there is some value in maintaining a distinctive French culture and identity, but it is not valuable enough to justify forcing millions like Marvin to starve. Moreover, libertarians deny that immigrants destroy culture. First of all, immigrants add to culture. As economist Bryan Caplan points out, America’s cultural centers (such as New York City and Los Angeles) have high immigration. Its “cultural wastelands” (such as North and South Dakota, Alaska, and Alabama) have low immigration. The economist Tyler Cowen might add: most “native” cultures are themselves the product of past cultural synthesis. The native cultures we want to preserve arose from past movements of people and their ideas. Libertarians respond to the second worry by pointing out that it flies against the consensus of professional economists who have studied the issue. Numerous economists have studied the effect immigration has on native wages. The most pessimistic of these studies tend to conclude that immigration only has a small (<5%) and short-term negative effect on the wages of low-skill native workers. These negative effects disappear after a few years. Other native workers’ wages increase. Immigrants do not usually replace native workers; instead, they bring in new skills and produce new jobs. Thus, even on the most pessimistic accounts, immigration helps most natives. It hurts only a small minority of natives, and it only hurts them a small amount for a small time. This is hardly enough to justify condemning the Marvins of the world to poverty, suffering, and death. Again, note that this is what the pessimistic studies say. In general, a majority of economists think that immigration increases wages for most people. Libertarians respond to the third complaint by saying that the facts do not back it up. Sociologist Robert Samson found that first-generation Mexican immigrants are only about half as likely to commit violent crimes as third-generation Americans (of any nationality). The economists Kristin Butcher and Anne Piehl find that immigrants are incarcerated at only 1/5th the rate of the native born. Given that immigrants tend to be poor, we should expect them to commit more crime, yet they do not. Native-born working class white people—people who themselves tend to oppose free immigration—are much more likely to go to prison than the immigrants they blame for crime. Libertarians conclude: Immigration does not appear to increase crime. Yet, even if allowing free immigration did increase crime, it would have to increase crime dramatically before that would justify condemning the Marvins of the world to poverty, suffering, and death.

When I discuss this with my classes, I point out that while high immigrant areas tend to be high crime areas, this doesn’t imply that immigrants cause the crime. Instead, it could be that immigrants live in high crime areas because these places are cheaper to live in, and immigrants tend to be relatively poor.

Libertarians have a simple response to the fourth objection: If we can’t afford to give immigrants welfare benefits, that doesn’t mean we shouldn’t let them immigrate. Instead, it means we should let them immigrate but deny them welfare benefits. However callous that may sound, it is far less callous than forbidding immigration. After all, in neither case do we pay them welfare benefits. Yet, when we allow them to immigrate, we greatly improve their welfare.

There’s a final objection, which I didn’t consider in the book: Open borders would cause massive political instability. Seems legit to me. After all, as we learned in high school, open borders caused the American civil war. But in all seriousness, I’ve seen this objection asserted, but rarely defended. So I don’t feel much need to refute it.