At Personal Finance, we have grown increasingly concerned with the national trend toward underfunded retirement plans. As a service to our subscribers, for the next few weeks we’ll send you a complimentary series of focused briefs to get you thinking about new ways to maximize performance both inside and outside of a structured 401k or similar plan. We hope you’ll find these briefs useful … if they are not applicable to your situation please click here to stop receiving the series.

This is the fifth installment in a five-part series.

Retirement assets can really add up, especially if you invest early and take advantage of employer perks such as company matching. So why are more men than women using 401k plans?

That’s the deal, as reported in a new study by banking giant Wells Fargo (NYSE: WFC).

Wells Fargo runs 401k programs for four million US workers, giving it valuable insights into the trends and habits among its army of would-be 401k Millionaires. The bank’s data points to a plan participation gap between men and women.

According to the report:

In a review of data compiled from 2,036 companies where gender was indicated, about half of all men (49 percent) and four out of 10 women (43 percent) are enrolled in their workplace retirement plan. When compared to Wells Fargo’s recommended contribution index, which measures how many people are saving a minimum target of 10 percent in their 401k plan, including employer match, 43 percent of men contribute at this rate versus 39 percent of women.

Even a 4 percent gap in gender 401k plan participation rates can cost women savers real money.

Wells Fargo points out that plan participants who contributed to their 401k plans saw their average balances rise 19 percent and 35 percent over the past two years, largely due to stock market gains.

“In general, all men and women need to take full advantage of their workplace retirement plan and embrace the 401k as the primary retirement benefit,” explains Joe Ready, director of Wells Fargo Institutional Retirement and Trust. “In our view, if people have access to a 401k they should try to save at least 10 percent. The power of saving regularly, coupled with the compounding effect of time, can create a financial foundation for people that results in much greater retirement security.”

Compounding, often dubbed the “miracle of compounded interest” allows 401k plan money to grow steadily over time, especially if you keep plowing money into your plan, and don’t take any of it out before retirement.

Your plan assets grow as the underlying stocks, bonds and mutual funds earn positive returns. And with the last two years seeing market growth rates of 19 percent and 35 percent, respectively, that’s a load of compounded interest.

One takeaway from the Wells Fargo study is that not only are men more likely to participate in a 401k plan, they’re more aggressive with their investment choices. In contrast, women are more likely to diversify their investments and spread risk among different asset categories – say, a minimum of two equities and a fixed fund and less than 20 percent in employer stock – in their 401k account investments.

It’s not an alarming gap, but the difference in 401k participation rates between men and women bears watching. If it grows wider, female 401k investors may face a bigger uphill climb to financial security than their male counterparts.