Mercer's new "What's Working" survey, released Monday, found 32 percent of U.S. workers are "seriously considering" leaving their job. That's a sharp jump from 23 percent reported in 2005.

Meanwhile, another 21 percent are not looking to leave but view their employers unfavorably and have "rock-bottom scores on key measures of engagement, a term that describes a combination of an employee's loyalty, commitment and motivation," according to a Mercer press statement.

"The business consequences of this erosion in employee sentiment are significant, and clearly the issue goes far beyond retention," said Mindy Fox, a senior partner at Mercer and the firm's U.S. region leader. "Diminished loyalty and widespread apathy can undermine business performance, particularly as companies increasingly look to their workforces to drive productivity gains and spur innovation."