Open Borders — The Economic And Moral Case Examined

Michael Clemens did something unusual for an economist. He took a question that everyone assumed was "philosophical" and treated it as empirical. The question was: how much economic value is lost to the global barriers against labor mobility?

The answer turned out to be enormous.

Clemens' 2011 paper — the "trillion-dollar bills on the sidewalk" paper — synthesized decades of research on the "place premium." The place premium is the wage differential for doing the same work in different countries. A Mexican construction worker doing the same job as an American construction worker earns roughly four times less. Not because the Mexican is less skilled. Not because the Mexican works less hard. Because of the country the work is performed in. The Mexican worker moving north doesn't need new skills. They need different geography.

This place premium is not small. For workers from the poorest countries moving to the richest, it can be 15-20x. The global median estimated place premium across country pairs is around 3-4x. Aggregate this across the billions of workers globally whose labor is currently mispriced by the accident of where they live, and you get Clemens' headline number: removing labor-mobility barriers would roughly double world GDP. The range in the literature is 50% to 150% increase. Even the low end is larger than the total effect of every trade liberalization in the past fifty years.

For perspective, the World Bank's 2022 projection of what it would take to eliminate extreme global poverty was around $175 billion per year in additional aid. The gains from fully opening borders would dwarf that number by two orders of magnitude. We are, as a species, leaving something like $78 trillion per year on the floor.

Clemens' framing — trillion-dollar bills on the sidewalk — is deliberately provocative. In economics, there's a joke: two economists are walking down the street and one sees a hundred-dollar bill on the ground. The other says "don't bother, if it were really there, someone would have picked it up." The joke mocks the efficient-markets view. Clemens is saying: the bill is real. It's been on the sidewalk for centuries. The reason no one picks it up is political, not economic.

Bryan Caplan's book Open Borders (First Second, 2019, illustrated by Zach Weinersmith) makes the moral case in a form designed to be hard to dismiss. Here is the argument distilled.

Premise 1: Every human life has equal moral worth. This is the premise underneath nearly every respectable modern moral framework — liberal, religious, utilitarian, Kantian. You can disagree with it, but disagreeing puts you in a small and historically ugly minority.

Premise 2: If every human life has equal moral worth, then the accident of birth cannot justify radically different life prospects. The baby in Malawi and the baby in Switzerland both got unlucky or lucky through no merit of their own. Their future circumstances should not be determined by this lottery.

Premise 3: Current border policy is the primary global mechanism for enforcing the birth lottery. The Malawian baby is confined to Malawi's economy — at about 2-3% of Swiss GDP per capita — not by nature but by enforcement. Walls. Visas. Deportations. Coast guards. The accident of birth is made permanent by the deliberate use of state violence.

Premise 4: Current border policy therefore requires extraordinary moral justification, because it uses state violence to lock people into the economic conditions of their birth.

The argument then asks: what are the justifications offered for this? Caplan works through them. "Cultural preservation" — but cultures have always changed through migration and do not have moral standing equivalent to human lives. "Economic protection" — but the empirical evidence that immigration hurts native workers is weak and contested, and even where true, the harm to natives is a small fraction of the benefit to migrants and the aggregate economy. "Security" — but actual immigrants commit less crime than native-born citizens in basically every country that keeps statistics. "Welfare state" — this is the strongest objection, and Caplan concedes it has merit, but he argues it can be addressed through policy design (keyhole solutions) rather than wholesale exclusion.

The moral case is strong enough that most defenders of current policy have to retreat to something like "well, this is just how the world works" or "my country takes care of its own first." Those are positions. They aren't arguments. They're assertions that the accident of birth matters morally, which is the exact premise under contest.

Let me give the objections their full weight. The open-borders case is strong but not unanswerable.

1. The welfare-state objection. Milton Friedman, in a 1999 interview, said: "You cannot simultaneously have free immigration and a welfare state." He wasn't anti-immigrant. He was pointing out a fiscal reality. If a country offers generous public benefits to all residents, and anyone can become a resident, the benefit system gets overwhelmed. The math is hard to escape.

The open-borders response is usually some form of "keyhole solution." Grant work rights first, citizenship later. Bar new immigrants from certain means-tested benefits for a period. Tax them slightly differently. These are the kinds of policy designs that preserve the benefit of open movement without the fiscal crisis.

This is persuasive in theory. It's harder in practice, because tiered citizenship creates exactly the kind of second-class population that liberal democracies are supposed to avoid. Guest-worker programs in Germany, the Gulf states, and elsewhere have tended toward abusive conditions precisely because the guest workers lack political voice.

2. The cultural-absorption objection. Paul Collier, in Exodus (2013), argues that the pace and scale of migration matter enormously. A small flow of immigrants integrates. A large flow forms ethnic enclaves that can persist for generations. A very large flow overwhelms the receiving society's institutions and triggers political backlash.

Collier is not anti-immigration. He is arguing for managed immigration. The receiving society's culture — specifically, its high-trust institutions, rule of law, civic norms — is itself the prize that immigrants are moving toward. If you import people faster than those institutions can assimilate them, you risk degrading the thing that made the destination attractive in the first place.

This is a harder argument to dismiss than open-borders advocates typically admit. The empirical evidence on assimilation is mixed. Some waves integrate beautifully (Irish and Italian immigration to the US, 1880-1920, took two generations and produced cultural fusion). Others have stalled (some European guest-worker populations remain economically and culturally separate decades later). The variables that determine successful assimilation are not fully understood.

3. The wage-competition objection. The classic concern: immigrants flood the labor market at the low end, driving down wages for native-born workers who compete with them.

The empirical literature is huge and contentious. The consensus roughly is: there are short-run, localized wage effects on directly-competing workers, and these effects are real but small, usually in the 1-5% range. In the long run, the economy adjusts — immigrants consume goods and services, creating demand — and the aggregate wage effect disappears or becomes positive.

But "aggregate" hides distributional effects that are politically explosive. A small long-run wage hit on, say, native-born high-school dropouts without college degrees, concentrated in certain regions and industries, is enough to create a durable political backlash. The aggregate welfare math doesn't console the unemployed construction worker in Ohio. The open-borders case has to grapple with this distributional reality, not wave it away.

4. The xenophobic-backlash objection. Push open-borders policy too fast and you generate the political conditions for far-right movements that roll back not just immigration but liberal democratic norms generally. The 2015-16 Syrian refugee wave in Europe produced measurable increases in far-right vote share across the continent. Brexit was, among other things, a revolt against EU free movement. Trump's 2016 election was, among other things, a revolt against perceived immigration overreach.

The backlash is not a reason to abandon open movement. But it's a constraint on implementation speed. Move faster than political absorption allows and you get not open borders but harder borders, plus damage to democratic institutions.

Most careful thinkers on this question land somewhere in the middle. Here are the main positions, ordered from most cautious to most open.

Expanded legal immigration plus enforcement. Keep border controls, but raise the legal intake substantially. Shift from family-reunification priorities to skills-based priorities. Process asylum claims faster. This is roughly the Canadian model. It is modestly open-borders in practice while remaining fully within the nation-state framework.

Regional free-movement zones. The Schengen Area is the world's largest real experiment in open borders. 27 European countries. Around 450 million people. No passport controls within the zone. It has been running since 1995 and is, on net, a tremendous economic success. GDP gains, labor-market flexibility, cultural integration. It has been politically strained by the 2015 refugee wave and by Brexit, but it has not collapsed. ECOWAS in West Africa and MERCOSUR in South America have attempted similar but weaker versions. The East African Community is slowly building toward free movement.

The Schengen model matters because it proves the thing skeptics say is impossible is actually happening, at scale, for decades. It's not theoretical.

Guest-worker programs with citizenship pathways. Structured, legal labor migration with defined durations, work protections, and eventual eligibility for permanent residency. This is a middle path that captures most of the economic benefits of labor mobility while retaining some political control over flow rates.

Refugee resettlement at scale. Accept that the global refugee population is now over 100 million and build resettlement infrastructure at the scale that implies. This is morally defensible on its own terms and does not require the open-borders argument.

Caplan's full open borders. No immigration restrictions. Work, live, vote (eventually) anywhere. This is the endpoint. Nobody is implementing it. It exists in the discourse as the limit case — the policy that would fully honor the premise of equal human worth.

The 1,000-page manual puts open borders on the table not because we expect full implementation but because the extreme endpoint forces clarity. When you have only the middle positions to argue about, you can dress up a narrow worldview in the language of pragmatism. When you name the endpoint, you have to explain why you stop where you stop.

If you believe in human equality but you support border controls, fine. Tell me where you stop and why. Do you support legal migration expansion? If not, why not? Do you support refugee resettlement? If not, why not? Do you support Schengen-style regional zones? If not, why not?

Most people discover, when pushed, that their stopping point is roughly "the point at which additional immigration would be politically uncomfortable for me personally." That's a position. It's not a moral argument.

The 1,000-page manual is explicit about this: we are not prescribing open borders. We are refusing to let you off the hook of the premise. If you believe in Law 1 — We Are Human — you have to do the work of figuring out what that means at the scale of global movement. Open borders is the hardest version of that question. That's why it's in the book.

The birthright-accident framework. The strongest starting point for examining any global question is: this person did not choose where they were born. Apply that to every question about national policy, aid, trade, and migration. The frame by itself will not answer the question. It will rule out several bad answers that rely on treating the accident of birth as morally load-bearing.

The place-premium framework. The gap between what a person earns in their home country and what they would earn doing the same work elsewhere is a measurement of political violence — specifically, the violence required to prevent that person from moving. You don't have to accept this framing. But once you've seen it, you can't unsee it.

The keyhole-solution framework. For every objection to open migration, ask: is there a policy design that addresses the specific harm without blocking the entire flow? Welfare-state pressure can be addressed with tiered benefit eligibility. Wage competition can be addressed with sectoral rules or wage floors. Cultural absorption can be addressed with pacing and integration investment. Each of these is imperfect, but each represents moving the policy toward openness while addressing the specific concern that would otherwise prevent it.

The backlash-constraint framework. Any change to migration policy operates under a political-absorption constraint. The right rate of opening is the fastest rate that doesn't trigger backlash severe enough to reverse the gains. This is not a principled argument for slowness. It's a practical argument for sequencing.

- Michael Clemens, "Economics and Emigration: Trillion-Dollar Bills on the Sidewalk?" Journal of Economic Perspectives 25:3 (2011), pp. 83-106. - Bryan Caplan and Zach Weinersmith, Open Borders: The Science and Ethics of Immigration (First Second, 2019). - Alex Nowrasteh, work at the Cato Institute on immigration and its economic effects. See especially Wretched Refuse? The Political Economy of Immigration and Institutions (with Benjamin Powell, Cambridge, 2020). - Paul Collier, Exodus: How Migration Is Changing Our World (Oxford, 2013). The most serious skeptical work. - George Borjas, We Wanted Workers: Unraveling the Immigration Narrative (Norton, 2016). The leading economist making the wage-competition case. - Branko Milanovic, Global Inequality: A New Approach for the Age of Globalization (Harvard, 2016). On how much of global inequality is explained by country of birth (answer: about two-thirds). - World Bank, Migration and Development Brief series. Ongoing data on remittances, migration flows, and economic effects. - The OpenBorders.info wiki, maintained by Caplan and others, is the best free compendium of arguments on all sides.

1. Find your stopping point. Write down the most open migration policy you would actually support. Then write the reasons you wouldn't go further. Inspect those reasons honestly. Are they moral or are they about personal comfort?

2. The Schengen thought experiment. Imagine your country joining a free-movement zone with its three closest neighbors. What changes? What works? What breaks? This is not hypothetical — it's what 27 European countries actually did.

3. The place-premium for someone you know. Pick a person in your life from a poorer country. Estimate what they would earn doing their current work in a rich country. The number is usually shocking. Sit with it.

4. Read the strongest opponent. If you already lean open-borders, read Paul Collier's Exodus carefully. If you lean closed-borders, read Caplan and Clemens. The objections to your own view are almost always more serious than you assume.

5. Talk to a recent immigrant. Not to argue policy. To understand what the experience actually is — what they crossed, what they gave up, what they're building. The abstraction of policy debate tends to dissolve in actual contact.

If every person said yes — if the assumption that people should be confined to the country of their birth dissolved — the world would not be chaos. It would be something closer to what the world was for most of human history, before the passport regime crystallized in the twentieth century. People would move toward opportunity and away from danger. Rich places would grow. Poor places would lose workers and gain remittances. The global economy would, over a generation, roughly double.

The reason we don't do this is not that it's impossible. It's that the psychology of national enclosure is still strong enough that the benefits — vast, measurable, aggregate — are outweighed politically by the costs — concentrated, visible, immediate. That's a real political problem. It's not a refutation of the moral case.

Law 1 is we are human. Open borders is what that law looks like when you run it all the way through the global labor market. You don't have to endorse the endpoint. You do have to know where you stop and why.