Because of ObamaCare, that is. This is from Casey Mulligan in the New York Times (Hat Tip John Goodman):
Work incentives for low-wage workers are eroded more than 10 percent of their compensation over the next couple of years, compared with 5 percent for midwage workers. Before the Affordable Care Act, the compensation for each additional hour of work by a low-wage worker, as with midwage workers, was split 50 percent, on average, for employee and 50 percent for the government. Under the law, it will be 39-61.
