The case for opening borders

The overwhelming majority of would-be immigrants want little more than to make a better life for themselves and their families by moving to economic opportunity and participating in peaceful, voluntary trade. But lawmakers and heads of state quash these dreams with state-sanctioned violence—forced repatriation, involuntary detention, or worse—often while paying lip service to “huddled masses yearning to breathe free.”
Wage differences are a revealing metric of border discrimination. When a worker from a poorer country moves to a richer one, her wages might double, triple, or rise even tenfold. These extreme wage differences reflect restrictions as stifling as the laws that separated white and black South Africans at the height of Apartheid. Geographical differences in wages also signal opportunity—for financially empowering the migrants, of course, but also for increasing total world output. On the other side of discrimination lies untapped potential. Economists have estimated that a world of open borders would double world GDP.
Even relatively small increases in immigration flows can have enormous benefits. If the developed world were to take in enough immigrants to enlarge its labor force by a mere one percent, it is estimated that the additional economic value created would be worth more to the migrants than all of the world’s official foreign aid combined. Immigration is the greatest anti-poverty program ever devised.

Alex Tabarrok makes the case for opening borders, and it's a strong one. The ultimate NIMBY-ism isn't at the city level, it's at a national level. “Give me your tired, your poor, your huddled masses yearning to breathe free,” but just a few of them, the rest, the masses, they're on their own.

I would not be where I am today had my parents not come to the United States from Taiwan when my dad entered graduate school. Go back further, and my parents were lucky to be able to migrate to Taiwan during the turmoil in the 50's in China. I'm entirely the product of a long line of good fortune.

As noted in Good Luck Being Born Tomorrow, which I've linked to before:

97% of people born tomorrow will be in a country that is authoritarian, communist, doesn’t support same sex marriage, does not allow abortion, supports capital punishment or has seen over ten thousand deaths in recent armed conflicts. Good luck!

If you were reborn tomorrow, assigned randomly to be one of the babies born somewhere in the world, your odds of being as fortunate as you are now (I assume you are one of the lucky ones given you're reading this post) are worse than the odds of flipping a coin and drawing heads. A lot worse.

To believe that those not as fortunate deserve no chance to improve their lot, that takes a deep sense of privilege. As Tabarrok notes:

What moral theory justifies using wire, wall, and weapon to prevent people from moving to opportunity? What moral theory justifies using tools of exclusion to prevent people from exercising their right to vote with their feet?
No standard moral framework, be it utilitarian, libertarian, egalitarian, Rawlsian, Christian, or any other well-developed perspective, regards people from foreign lands as less entitled to exercise their rights—or as inherently possessing less moral worth—than people lucky to have been born in the right place at the right time. Nationalism, of course, discounts the rights, interests, and moral value of “the Other, but this disposition is inconsistent with our fundamental moral teachings and beliefs.
Freedom of movement is a basic human right. Thus the Universal Declaration of Human Rights belies its name when it proclaims this right only “within the borders of each state.” Human rights do not stop at the border.Today, we treat as pariahs those governments that refuse to let their people exit. I look forward to the day when we treat as pariahs those governments that refuse to let people enter.

Market argument for immigration

Bryan Caplan lays out his most succinct defense of immigration yet.

1. Open borders are an extremely important component of the free market and human liberty.  The labor market is roughly 70% of the economy.  Labor is the main product that most people around the world have to sell.  Immigration restrictions massively distort this market, and deprive literally billions of people of the freedom to sell their labor to willing employers.  So even if open borders made all other policies much less pro-market and pro-liberty, the (open borders + side effects thereof) package would almost certainly constitute a net gain for free markets and liberty.

Click through to read the rest of his argument, and the discussion thread. Economics blogs tend to have more sane, less belligerent commenters than most sites.