Marcial Reyes could have just quit his job. Frustrated with chronic understaffing at the Kaiser Permanente hospital where he works in Southern California, he knows he has options in a region desperate for nurses.

Instead, he voted to go on strike.

And many of them are either hitting the picket lines or quitting their jobs as a result.

The changing dynamics of the US labor market, which has put employees rather than employers in the driver's seat in a way not seen for decades, is allowing unions to flex their muscle.

Twenty years ago today, on a Sunday afternoon in Brookwood, Alabama, 32 coal miners descended 2,000 feet below the ground into the Jim Walter Resources Blue Creek No. 5 Mine for a routine maintenance check.

Flying into Phoenix Sky Harbor International Airport recently, I spotted the ramp workers on the tarmac, busily unloading bags and doing safety checks on the plane in 115 degree heat.