This excellent post by Bryan Caplan, professor of economics at George Mason University, was originally featured at OpenBorders in January of 2013. Below is an excerpt.

I changed my mind about proper immigration policy in my senior year of high school. The impetus, as usual for me, was not first-hand experience, but abstract argument. After reading Ayn Rand’s Atlas Shrugged, I became a vociferous libertarian. Given this orientation, I converted to open borders as soon as another libertarian pointed out that free immigration is just free trade applied to labor. If memory serves, Murray Rothbard’s Power and Market, chapter 3, section E was the pivotal discussion for me.
Still, I was too factually ignorant to grasp the enormity of the issue. I saw no reason to take immigration restrictions more seriously than, say, steel tariffs. I didn’t realize that immigration restrictions are far more onerous than trade barriers on steel. I falsely assumed that illegal immigration to the U.S. was pretty easy. I didn’t realize that the labor market is by far the largest market in the world – roughly 70% of national income. I didn’t realize that immigration restrictions trap hundreds of millions of people in Third World poverty.
The corollary, of course, is that I didn’t realize that open borders would drastically change every aspect of our society. Basic economics says that free immigration would drastically increase global wealth and drastically reduce global inequality. But basic psychology says that visibility of the remaining poverty and inequality would sharply rise. (The sobering implication is that even if open borders works as well as I expect, many First Worlders will angrily call it a disaster).
Given my ignorance, I was able to intellectually embrace open borders without taking the issue seriously. In high school and college, I spent far more time debating epistemology than immigration. When I tried to convert others to open borders, my main empirical argument was to point to America’s experience with virtually open borders in the 19^th century. If free immigration was great then, why not now?”]
For the rest of this article and more great resources on open borders check out OpenBorders. What do you think about America’s immigration policy? Are you an advocate of open borders? Let us know below!