Investors saving for retirement face many obstacles, including high fees, poor investment options, vanishing pensions and even outright fraud.

However when workers pass up an offer of essentially free money with no strings attached, it's hard to identify a scapegoat other than those workers.

I recently learned that more than 56,000 Boeing employees fall into that category. Apparently they’d rather give billions of dollars to Boeing BA, -3.95% shareholders than keep the money for themselves.

Mighty generous.

I came across a notice to Boeing employees informing them that they collectively left $98 million on the table in 2013 by not taking advantage of matching funds in the company's 401(k) plan.

According to this report, approximately 8,400 Boeing employees declined to participate at all in the program last year, and another 48,000 "didn't contribute enough to receive the maximum company match." Boeing didn’t respond for comment but my hat’s off to them for being so forthcoming with their employees.

It's startling to realize that about a third of all Boeing employees are voluntarily taking less pay than the company wants them to have. To receive the full company match, employees would only need to contribute 8% of their base pay.

Boeing matches those contributions at the rate of an extra 75 cents on the dollar. In other words, set aside $1 and get an instant one-time-only return of 75%.

I don't know why employees are passing up this opportunity. Undoubtedly many of them are relatively young and struggling to make ends meet. Probably many are waiting for a time when they can afford to put money into the 401(k) plan that Boeing calls VIP, for Voluntary Investment Plan.

I think it's a safe bet that by and large Boeing hires brighter-than-average workers. (Anyone who flies across the continent or across the ocean had better hope so!)

However, I think many of these employees have failed to do some simple math. Here's an example:

An employee with a base pay of $60,000 is eligible to earn a 75% match on up to $400 a month. The monthly match, $300, amounts to a raise in pay of $3,600 a year. That's the equivalent of a 6% raise — something I doubt employees would turn down if it were offered to them in those terms.

Here's another example: The $98 million left on the table is only for a single year. Multiply that by a decade and you have nearly $1 billion these employees never got.

Invest that $1 billion for a mere 20 additional years and it could easily grow to be worth five times that much. These of course are extremely conservative numbers because most people work longer than 10 years and invest for more than 20.

But here's the real math: $5 billion is worth 50 times as much as the $98 million that Boeing gave its shareholders last year because some of its employees didn't want the money enough. And that doesn't take into consideration the future value of the employees' own savings — an even higher number.

I used Boeing as an example but they’re hardly alone.

A survey conducted this year by Harris Poll for Wells Fargo found that middle-class U.S. residents aged 25 to 75 have set aside a median of only $20,000 for their retirement. One-third of them reported they are not contributing at all to a 401(k), an IRA or any other retirement plan — that's far worse than the Boeing statistics.

Of those who are saving, the median amount reported was $125 a month.

About half of those who were in their 50s told the pollsters they expect to work until age 80 because they will have inadequate savings to retire.

Overall, more than seven out of 10 who were polled said they now believe they should have started saving earlier.

To that, I say Amen!

We can't change our past, but most of us can change our future if we change what we're doing now.

Here's how to start:

First, do the math. How much will you need to retire? Here's an article to help you get going.

Second, how will you obtain that much money? (I promise you it won’t fall from the sky.)

Third, make sure you are getting all the pay (matching funds) that your employer wants you to have.

Fourth, if you find it hard to cut back your spending to save money for the future, don’t give up until you have a serious conversation about this with your family members. Are they willing to give up a few things now so all of you can live better later?

If you tackle this seriously, with the help of an independent financial adviser who doesn't sell products, you are likely to wind up ahead of the game.

Richard Buck contributed to this article.