From American Prospect:
When a Wal-Mart opens in a new territory, it either drives out the higher-wage competition or compels that competition to lower its pay. David Neumark, an economist at the University of California, Irvine, has shown that eight years after Wal-Mart comes to a county, it drives down wages for all (not just retail) workers until they’re 2.5 percent to 4.8 percent below wages in comparable counties with no Wal-Mart outlets.

For the full story, please visit http://prospect.org/article/40-year-slump.