The job market's strength — unemployment fell to a seven-year low of 5.4 percent in April — has proved to be a boon for American workers.

"Companies are scrambling to hold on to workers amid a tightening labor market and higher turnover, doling out bigger raises, expanding benefits and providing more training and other perks," writes Paul Davidson of USA Today.

"They're awakening to the fact that they're going to lose their people," Paul McDonald of job agency Robert Half told the paper. "We're seeing an increased investment in the employee."

He said 30 percent of his clients are offering raises to workers who plan to leave, up from 20 percent a year ago.

Worker compensation, including benefits, climbed 2.6 percent in the first quarter, the most since 2008.

Meanwhile, approximately one-third of companies are reinstating or raising bonuses, and 50 percent are increasing spending on training and development, according to a survey of CFOs by Robert Half's Accountemps unit.

But not everyone is impressed with the labor market's signs of strength. Beneath the surface, trouble lies, says financial writer Elaine Pofeldt.

"Tucked away in the pages of a new report by the U.S. General Accounting Office is a startling statistic: 40.4 percent of the U.S. workforce is now made up of contingent workers — that is, people who don't have what we traditionally consider secure jobs," she writes in an article for Forbes. That's up from 30.6 percent in 2005.

The contingent workers include:

• Agency temps: 1.3 percent
• On-call workers: 3.5 percent
• Contract company workers, 3.0 percent
• Independent contractors: 12.9 percent
• Self-employed workers: 3.3 percent
• Standard part-time workers: 16.2 percent

Pofeldt says the data raise more questions than answers.

"Do we revamp our social safety net to reflect the fact that so many millions of Americans are untethered from employers who once provided security? Should we crack down on businesses that try to avoid paying a living wage? Should we revamp our education system?"

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