From the article:
"...Trapping immigrants in low-productivity countries results in huge losses not just for them but for global productivity. How huge? The Center for Global Development's Michael Clemens has estimated that if everyone could take a job anywhere they wanted, our $75 trillion global world product would experience an instant boost of 50 to 150 percent annually. Using the lower number would mean adding $37 trillion of wealth to the world. Even if you discount Clemens by 50 percent, we are still talking of $17 trillion, or the size of U.S. economy, added to the world every year, which would end global poverty while enriching First World natives.
Even the meager immigration the U.S. has allowed has made this country immensely richer. Reasonable estimates suggest that the total annual contribution of foreign-born workers to the U.S. economy adds up to roughly $2 trillion, or about 10 percent of annual GDP. Optimistic ones put that number higher. And even an immigration pessimist like Harvard University's George Borjas puts it at $1.6 trillion."
