Not every employee is the best manager of his own retirement fund, even if he faithfully contributes to his 401(k).

Like Gil Thibeau, Winson Crabb, 68, took advantage of National Semiconductor's retirement plan and received employer matching -- dollar-for-dollar, up to 6 percent of his salary -- every year for 16 years. But when Crabb retired from National in 2003 and cashed out his 401(k), what he thought would be a nest egg of $120,000 turned out to be closer to $52,000. After paying taxes and debts, he was left with $26,000 to stretch over an estimated life expectancy of 20 years.

How can two employees with the same company, regularly contributing to their retirement funds, have such different experiences?

One key difference is that Gil Thibeau earned about twice as much as Winson Crabb and was therefore able to save more. But Thibeau succeeded in squirreling away nearly five times his annual salary, whereas Crabb, who earned roughly $45,000 a year, had accumulated less than one and one-half times his salary at his account's peak.

Crabb and Thibeau are an example of what benefits consultant Brooks Hamilton has labeled "yield disparity." The trend, observed in many 401(k) plans, is that employees with higher salaries also see the best return on their investments. The result is a widened gap between the highest and lowest paid workers, even in the same 401(k) plan.

Crabb might have narrowed the gap had he taken a more active role in managing his account. "A lot of people checked their accounts regularly, weekly, online. I never bothered because it was [an] outta sight, outta mind kind of thing with me," he says.

"I knew I was putting x amount of dollars in a 401(k). My assumption was that when I got to be 65, there would be a large amount of money in there for me to take cash out to put in our bank to utilize for whatever." Crabb, who worked the night-shift, also missed the company-sponsored retirement seminars.

The Crabbs also committed the cardinal sin of 401(k)s: They withdrew money from their account early to pay for their daughter's medical training. "The first time, I took 20,000 out, and that was a mistake," admits Crabb. "You never want to take out of a 401(k) until you get ready to use it at the end, when you're retirement is ready."

The Crabbs managed to replace the $20,000, but then took out another $10,000. "I had to have me a motor home," explains Winson. Ultimately, they were forced to sell the motor home because maintenance costs were too high.

Nonetheless, as Winson approached retirement, he and his wife Bess thought they would have about $120,000 in their account. But the stock market downturn over 2000 and 2001 cut their account balance in half. "At that point in time, it was really too late to do a whole lot about it," says Winson, who was 62 years old at the time. "We've never been one to just cry in our beer," he explains. "We just said, 'Well, that's where we're at in life right now, so we'll continue on from here.'"

The Crabbs made another wrong turn by withdrawing the 401(k) in a lump sum. "What I should've done was roll it into a IRA and take a monthly payment on it," he says. Instead, he took the full amount in cash and had to pay higher income taxes on it. After paying the taxes and a few outstanding debts, the Crabbs were left with just $26,000.

"I really didn't realize at the time how much it was going to cost me to do that," says Winson. "It was a jolt. You know, one day we had to set down and say, 'Whew! This is not like what we thought.'"

Fortunately, Winson also has a traditional pension through his steamfitters union, $800 a month for 35-years of service. But already accustomed to how insecure benefits can be, he opted for an annuity of $400 a month for his and Bess' lifetimes. "I mean, that's not a hell of a lotta money, but it's secure," he says.

But $400 a month, plus Social Security, was not enough for the Crabbs to maintain their standard of living, especially with the high cost of health insurance. Although Winson qualified for Medicare, Bess Crabb had to return to work, just like Gil Thibeau, to earn employer-sponsored health insurance.

Today, three years after retiring from National, Winson has found that he, too, needs to reenter the workforce, and he has signed up for a six-month stint as a safety officer at a chip plant in Albuquerque, 600 miles away from home.

Still, Winson is sanguine about having to work as he approaches 70. "I think this is something that many people in the United States are realizing," he says. "But I hope at least some of them will enjoy it as much as I will." Bess Crabb is less cheery. "I thought, when he retired, it was going to be a lot different, you know -- money-wise," she says. "We lost a lot of, well, I won't say 'luxury items' that you buy … [but] all of a sudden, you have to think about it. You have to say, 'Do I want [this]?' 'Do I need this?' 'Do I really need this?'"

Winson, too, has had to make some painful decisions. A gun collector since he was 8 years old, he was forced to sell some of his guns: "[It] broke my heart," he says, "That was like taking a part of my liver out or something."

Despite their difficulties, the Crabbs are proponents of defined contribution plans. "I advise my children that 401(k) is OK -- it's a good program," says Bess Crabb. "But … that it's very important to know money management. We learned ourselves from experience."

Winson feels that he just didn't know enough about the whole process to make wise decisions about his money: "If I'd had the right information furnished me by National [Semiconductor's] 401(k) people, I would've done something different, because anybody would be stupid not to."