Government will then have no need to define or interpret rules about asylum, economic hardship, family reunification, family separation, DACA (Deferred Action for Childhood Arrivals) and so on. When all immigration is legal, these issues are irrelevant.

The question of fairness about who enters first — those who waited in line or those who entered illegally — disappears. Amnesty for existing illegal immigrants also becomes a non‐​issue. Or an open borders policy could require anyone who entered illegally to exit the country — for exactly five minutes — and then re‐​enter legally.

Think about the money we could save and make

Expenditure on immigration enforcement would shrink to nothing, because open borders means no walls, fences, screening at airports, ICE (Immigration and Customs Enforcement), deportations, detention centers or immigration courts. A 2013 report estimated that immigration enforcement cost more than $18 billion annually, and standard indicators suggest costs have grown further since then.

Last year, U.S. employers filed over 336,000 petitions for H1-B visas for highly skilled foreign workers, but only 197,129 were approved. Complicated visa rules — for tourists versus job‐​seekers, STEM (science, technology, engineering and math) workers versus agricultural laborers, and students versus non‐​students — would all vanish. This would save resources and give employers new access to talented human capital.

The time people waste re‐​entering the country will evaporate. How often do you face long delays when entering Oklahoma from Texas? Never. But how often do you experience delays when you leave other countries for the United States? Almost always. One study pegs the cost of wait times at the U.S.-Mexico border alone to be more than $12 billion a year.

Economic efficiency will increase both in the USA and in immigrant‐​sending countries, because different kinds of labor will be better matched around the world to their most productive activity. This benefits the immigrants who earn higher incomes, but also U.S. consumers who face lower prices for imported goods and services. One academic study predicts that if borders were open everywhere, world gross domestic product could be twice its current value.

They will send their best

The government’s fiscal balance could actually improve with more legal immigrants earning income and paying taxes in America. And under open borders, any added immigration will plausibly come from those with even higher skills and incomes, who faced weaker incentives to immigrate when faced with the burden of current restrictions.

Expenditure on the welfare state will contract because even if immigrants vote for welfare spending, existing residents will vote for less generous benefits when they believe these accrue to recent immigrants.

What about possible bad outcomes of open borders?

Immigrants will not flood into America, although the rate of immigration might increase. Instead, much of the immigration will be temporary. Return migration happens because most people want to be near their families, surrounded by their own language, culture or religion.

If immigrants know they can re‐​immigrate, they are less likely to put down roots. Instead, many will come for a few years, to work or study, and then depart. This happens routinely in the European Union, which has mainly abolished immigration restrictions among member states, and it was common historically during periods of relatively open borders. Plus, increased immigration will lower wage differentials across countries, reducing the incentive to immigrate.

Crime will not skyrocket. Available evidenceshows that immigrants are no more crime‐​prone than natives. And the additional immigrants likely to enter under open borders would plausibly be even less so, because they have shown respect for the law by not immigrating illegally.

Terrorists could well enter via open borders, but they do so now illicitly. Little evidence suggests that our immigration restrictions prevent terrorist attacks.

U.S. culture will not change dramatically. America’s immigrants have a long history of assimilation, and most have at least some affinity for American values. Indeed, the world is already more “Americanized” than ever. Even if values and culture change, so what? That happens in free societies. Who says America’s current values — some of them deeply evil — are the right ones?

Open borders are not without risks. Social safety nets might come under pressure, and natives will face added competition for jobs (though the evidence on this is mixed).

Ultimately, immigrants have always been vital to America’s economic strength and to its commitment to freedom. Since its founding, the United States has grown from a motley collection of colonies to one of the richest countries in the world, with some of our fastest growth occurring when immigrants arrived in large numbers.

America has nothing to fear, and much to gain, from open borders.