Early in my professorial career, I read Lant Pritchett's short book Let Their People Come: Breaking the Gridlock on International Labor Mobility. It convinced me that reducing immigration restrictions was an economic and moral imperative. Michael Clemens of the Center for Global Development called immigration "The Biggest Idea in Development That No One Really Tried" and suggested the world is leaving "trillion-dollar bills on the sidewalk" by restricting immigration so severely. About a decade later, immigration is still the biggest idea that one really tried, and the trillion-dollar bills remain on the sidewalk despite an emerging consensus that more immigrants-even immigrants who are in the country illegally-do not threaten our earnings or our jobs. By restricting immigration, Americans are lowering their standards of living so that they can lower others' standards of living, as well.

An immigration skeptic might call this an unfair characterization. Maybe immigrants don't lower wages or reduce employment, he says. Immigrants do, however, pose a threat to our liberty and security. It's crazy to suggest we should let in so many people from "sh*thole countries" because they'll just ruin our country by bringing the institutions and culture that ruined theirs.

On the very last page of their book, Wretched Refuse?, Alex Nowrasteh of the Cato Institute and Benjamin Powell of the Free Market Institute at Texas Tech University write, "Empirical conjectures require empirical evidence." They take the institutions-and-culture objection seriously by taking it to the data, and after it is tried and measured, it is found wanting. Immigrants, it turns out, aren't likely to take our freedom, destroy our culture, or compromise the political, economic, social, and cultural institutions responsible for that freedom and culture. 

In a series of careful quantitative analyses, Nowrasteh and Powell decisively shift the burden of proof. With the publication of Wretched Refuse? immigration skeptics should no longer be able to get by with speculation and anecdotes. They will need carefully-analyzed data to refute Nowrasteh and Powell's conclusion that immigrants don't harm or even slightly improve institutions in the immigrant-receiving countries. Immigration liberalization is about as close as we can get to a magic-wand policy. By letting more people cross borders to find work and housing, we rich Westerners can effectively end severe poverty and make ourselves much better off in the process.