Readers have been sending me the best links. Here's one from the latest issue of Newsweek:

As the white house revives immigration reform--an issue the president is
discussing with congressional leaders--it may want to ponder the effects
of curbing foreign labor. While immigrants are blamed for dragging down
American wages and stealing jobs, University of California, Davis,
economist Giovanni Peri comes to a different conclusion. In a National
Bureau of Economic Research working paper, Peri trowels through nearly
five decades of immigration data and finds that foreign workers have
boosted the economy, jacking up average income without crowding out
American laborers. For each percentage of the workforce that is
foreign-born, he found an almost 0.5 percent bump in average wages. In
California, where the percentage of immigrants in the workforce has
jumped more than 25 points since 1960, that means an almost 13 percent
bonus--roughly $8,000. Immigrants, Peri says, push native-born workers
into better-paying positions, expanding the size of the job pie so
unskilled Americans aren't left out.