Though women are just as optimistic as men about the stock market, they are much less confident about their investment decisions, according to a survey by the retirement division of Massachusetts Mutual Life Insurance Co.

This lack of confidence may lead women to shortchange themselves in the long run by investing less in retirement savings plans than men do.

Elaine Sarsynski, an executive vice president in the retirement services division and chairman and CEO of MassMutual International LLC, explained by e-mail: "At MassMutual the average savings rate for men is 5.76%, and for women it's 5.35%. Average account balances for women are about 63% of those of men. These statistics reflect the need to drive more women to save in defined contribution/401(k) plans and then help them allocate appropriately and with confidence."

The online survey of more than 1,000 of its retirement plan participants between Nov. 15, 2009, and Jan. 15, 2010, showed that, though women and men were equally optimistic about the market outlook, only 32.5% of women were confident about their own investment decisions, compared to 47.8% of men.

But men's confidence about investing is usually overconfidence, Mike Alfred, the chief executive at BrightScope, an independent provider of 401(k) ratings and financial data to plan sponsors, advisers and participants, said in an interview Wednesday. "Which is why a lot of studies say that women are really better investors than men, because men are trying too hard to beat the market, which, as most people are now aware, is a fool's game."

The survey also said 61.5% of men enjoy managing their investments, compared to 48.1% of women, and that more women prefer to spend as little time as possible on investment decisions, compared to men.

Sarsynski added that being able to fund retirement is a concern for 37.3% of 401(k) participants — more than double the rate of concern expressed about health-care costs, 16.0%; job security, 14.5%, or managing debt, 12.2%. "While almost nine times as many participants believe that they need to save more for retirement as don't (72.9% vs. 8.2%), women are more concerned that they won't have enough saved (70.3%) compared to men (63.2%)," she said.

Another difference between the sexes, Alfred said, is that women are more willing to take good advice. "Men usually go back and read three more things and want to talk them all," he said.

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