One in five Americans plans to retire before age 65, according to a new study, and they're not just the ultra-wealthy. There's hope for everyone to bail out of the daily grind before age 65, if they adopt the behaviors and attitudes of these savers.

The Transamerica Center for Retirement Studies, an organization funded in part by the Transamerica Life Insurance Company, surveyed more than 4,000 U.S. employees and delved deeply into the responses of the group they label "future early retirees."

"We had two hypotheses: They were privileged and ultra-affluent or wildly optimistic," says Catherine Collinson, president of the center. But just 52% of the future early retirees had a college degree, and 49% reported an annual household income of less than $100,000. They are equally divided among men and women; half are over age 40.

"They are far more likely to be like the 'Millionaire Next Door' than a Bill Gates or Warren Buffet," Collinson says, referring to the 1996 best-selling book that found many U.S. millionaires lead relatively modest lifestyles. 

The future early retirees weren't pathological optimists either. The study authors extrapolated from the data on their savings behavior, and found they were actually "well on track to meet their goal," she says.

So who are the future early retirees, and why are they successful? They started saving earlier -- age 25, on average, versus age 30 for their later-retiring peers. They contribute more to their company plans -- 10% of income on average, versus 6% for other respondents. They are much more likely to save for retirement outside of workplace plans -- 69% versus 60% of those planning to retire after 65. 

They're also luckier: While about three-quarters of those surveyed enjoyed access to a company 401(k) plan, the future early retirees were more likely to have company-funded pensions as well (25% versus 14% for those...