We used to describe our country as a "great American melting pot," welcoming immigrants and the contribution diversity makes to our collective well-being. But these days it seems like more of us are disparaging immigration rather than celebrating it. Arizona has passed a tough anti-immigration law that could make life difficult even for legal immigrants. Republican Senators Lindsey Graham and Jon Kyl have proposed revoking birthright citizenship--a move that would require amending the constitution.

But what are the realities of immigration? Well, let's start out with just how many foreign-born people are in the United States. Estimates suggest that non-natives compose

15.6 percent of the work force

That's nearly one out of every six workers. And, as the chart below shows, this fraction is the highest it's been since "labor force" included anyone over the age of 10 who was gainfully employed. 

Of course, we have a long historical tradition of welcoming immigrants, and we have benefited from their ideas and labor. This week, we'll try to get a better sense of what kind of impact these immigrants are having--and not having...