(ARA) That promising new employee starting next week brings skill and adaptability to the job — and he also sports some gray hair, or none at all.

Workers aged 55 and older will be the fastest growing age group in the American workforce in the next two decades, according to the Department of Labor. Their share of the labor force will increase from 13 percent in 2000 to 17 percent in 2010. By 2020, one out of every five workers is expected to be older than 55.

For every three boomers that leave the workforce, there are but two younger workers waiting in the wings to replace them. “To cope with this scarcity of workers, companies that want to stay competitive will be forced to implement innovative strategies to attract and retain older workers,” says George Corona, senior vice president at staffing provider Kelly Services. “Older workers typically offer an organization a greater bank of skills, fewer commitments, more financial stability and broader experience.”

There is no medical proof that worker productivity decreases with age, notes Corona. “If someone does not perform well at age 55, then they probably did not perform well at age 35 either.”

In fact, a recent study by the Employee Benefits Research Institute says that nearly two out of every three workers expect to continue in gainful employment after they “retire.” “Many of the older workers we place haven’t lost their work ethic, and they often find the traditional retirement lifestyle boring and unfulfilling,” says Corona.

Many companies are adopting the concept of phased retirement — letting older workers gradually transition from full to part-time, while giving them partial access to pension and healthcare benefits. In fact, the Internal Revenue Service (IRS) is now considering modifying traditional pension and 401(k) savings plans to enable people to keep working while collecting full or partial benefits.