Want to see the future? Open borders.

Global restrictions on migration are holding the world economy back by two decades. The economic loss we suffer every single year as a result of governments’ arbitrary barriers on labor mobility is equivalent to the next 20 years of economic growth.

Simply put, lifting restrictions on immigration would double world GDP.We can get a headstart on the future by abolishing arbitrary restrictions on immigration today.

What does that mean in practical terms?

Gross Domestic Product (GDP) is the total value of all final goods and services produced within a country during a year. Basically, it is the amount of stuff being produced by your country–food, cars, clothes, legal advice, etc.–each year. GDP per capita means the total value of your country’s output divided by the number of people, and it’s often used as a rough measure of standard of living: the more stuff your country produces per person per year, the better off you are likely to be.

In 2013, total world GDP was $87 trillion. That’s about $13,100 for every person on the planet–all 7 billion of us. Obviously, people in rich countries have a bigger fraction than people in poor countries: GDP per capita in Norway is $55,400, while GDP per capita in Mozambique is $1,200.2

At an average annual growth rate of 3.5%, world GDP will have doubled in twenty years.3 If countries around the world lifted all barriers to labor movement (immigration and emigration restrictions), we could double world GDP. This means that relatively quickly, as people adjusted, we could be producing twice as much wealth each year. As labor moved to the places it is most productive, we could all make (and consume) many more things, much more efficiently. Economically, we would leap twenty years into the future.

World GDP could be $174 trillion, about $26,200 per person. Twenty years from now, assuming average growth rates continue, world GDP could have doubled again, to almost $350 trillion. GDP per capita would more than double, because population growth rates are declining (and decline faster as countries get richer). Conservatively, GDP per capita in 2040 could be a lot higher for the average person around the world than it is for people in, say, Switzerland in 2013 ($46,000 per capita).

Moreover, most of this increase would accumulate among the world’s poor. They have the most to gain, simply by moving from poor, oppressive countries with lousy capital and infrastructure to richer, freer countries where their labor value would be much higher. Just by moving from Ecuador to the United States, a worker’s productivity increases by 400%. For identical workers in Nigeria and the US, moving to the US increases their productivity by a factor of fifteen.4

If you’re worried about being left out of this explosion of economic growth, you shouldn’t be: immigration helps immigrants, but it also helps the countries they move into. As Bryan Caplan put it, “If total world output doubles, your standard of living is very likely to rise. This isn’t ‘trickle-down economics’–it’s Niagra Falls economics.

The bottom line is this: if you care about economic freedom, if you care about economic growth, if you care about poverty, wealth, inequality, justice, the debt, the environment, or almost anything else except xenophobic identity politics, opening your borders to peaceful migration will help.

There are very few problems that could not be alleviated by having twice as much wealth produced each year. Wherever you are, whatever your reasons for opposing free migration, they are costing the world economy $87 trillion a year. They are holding the world back by two decades. Is it really worth it?

1  Efficiency gain, in percent of world GDP, from eliminating international barriers to labor mobility: Hamilton and Whalley (1984), 147.3%; Moses and Letnes (2004), 96.5%; Iregui (2005), 67%; Klein and Ventura (2007), 122%. Average of the four: 108.25%.
2  Estimates from the CIA World Factbook, in current US dollars, adjusted for purchasing power.
3  Estimated the average world growth rate since 2006. Source: IMF World Economic Outlook.
4  Clemens, Michael, Claudio Montenegro, and Lant Pritchett (2009).