A cohort selected for punishment by decimation was divided into groups of ten; each group cast lots (Sortition), and the soldier on whom the lot fell was executed by his nine comrades, often by stoning or clubbing. The remaining soldiers were given rations of barley instead of wheat and forced to sleep outside of the Roman encampment.
Because the punishment fell by lot, all soldiers in the selected cohort were eligible for execution, regardless of rank or distinction.
Apparently, it's used by modern day businesses too. This is from Washington Post, Tuesday, April 3, 2007, Fannie Mae Plans To Cut Workforce by David S. Hilzenrath:
Fannie Mae, the District-based mortgage funding company, plans to reduce its workforce by several hundred full-time employees by the end of this year, a company spokesman said.
The cuts are part of "an effort to streamline and improve productivity for our investors," Fannie Mae spokesman Brian Faith said.
The company employs the equivalent of about 6,500 full-time workers. About 5,300 are based in the Washington area.
Wikipedia goes on:
Decimation, as with any mass punishment technique, was assumed to inspire fear and resolve in the remaining troops. In practice, decimation could destroy the esprit de corps of the unit. Soldiers, seeing their comrades being slaughtered, not by the enemy but their own, could lose their resolve and trust in their commanders. The Byzantine emperor Maurikios (582-602) strongly warns against arbitrary punishments in the Strategikon, implying they do more harm than good for morale.
Modern day HRs don't consider Maurikios as an authority indeed. Here's one more couple of years later from Bloomberg, Fannie Cuts Hundreds of Jobs in Washington Office (Update1) By Dawn Kopecki, Jan. 23
Fannie Mae, the mortgage-finance company under federal control, cut several hundred jobs today at its Washington headquarters as it adds workers elsewhere to combat rising foreclosures.
Brian Faith, a spokesman, didn’t immediately have a precise figure for the cuts. Fannie, the largest U.S. mortgage-finance company, will add about as many employees to its loss-mitigation team in Dallas. The company has about 5,500 employees.