Via David Sirota comes this new study (pdf) by the Center for Economic and Policy Research documenting what most progressives already know: unionization benefits low-wage workers.
"Using national data for 2003 through 2007, we estimate that unionization raises ...
"Using national data for 2003 through 2007, we estimate that unionization raises the wages of the typical low-wage worker (one in the 10th percentile) by 20.6 percent, compared to 13.7 percent for the typical worker (one in the 50th percentile), and 6.1 percent for the typical high-wage worker (one in the 90th percentile)."
CEPR breaks the numbers down by state as well. In Illinois, the average hourly wage of union workers is 14.7 percent higher than non-union colleagues in the 30th percentile, 14.6 percent in the 50th percentile, and 10.8 percent in the 70th percentile.