DES MOINES, Iowa -- Workers have become more involved in retirement planning, but too often just one member of the family takes care of investments and strategy, leaving the spouse unprepared to take over if needed.

Fidelity Investments says 41 percent of the 648 couples surveyed in May handle retirement investment decisions together. That means just one person, usually the husband, handles the retirement planning for a majority of families.

More worrisome is the fact that only 17 percent of couples say either spouse is prepared to assume sole responsibility of their retirement finances if necessary.

Women, who are more likely to survive their husbands, are not at all confident that they could take over. Just 35 percent of wives say they are completely confident in their ability to do so, while 72 percent of husbands say they can.

"The life expectancy for a woman on average is about three years longer than a man, so there's a likelihood that the wife will have to manage the retirement finances alone or at least be the primary decisionmaker at some point in time in retirement," said Chris McDermott, a senior vice president at Fidelity.

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Husbands and wives should know where critical documents are kept and what they would need to do if their spouse is no longer able to assist with financial decision-making. Both also should have an understanding of the family's finances and the savings and investment goals. They should become active in financial planning. Both should meet with the family's financial adviser.

The survey also suggests husbands and wives don't talk enough about fundamental facts of retirement living.