Historically the stock market returns approximately 9 percent a year, so you'd think that almost all of us would want to devote at least a portion of our investment portfolios to equities.

But 52 percent of Americans say they don't own any stocks or stock-based investments, such as mutual funds, according to a new Bankrate survey.

Of the 1,001 adults surveyed, 53 percent of those who don't invest in the market cite lack of money as the reason. Surprisingly, Millennials were the age group least likely to give that response (42 percent), versus those aged 65 or older (58 percent) who state they lack the savings to invest.

Other deterrents to investing in stocks include, not knowing enough about stocks to invest (21 percent), lack of trust in stockbrokers or advisers (9 percent), the stock market is too risky (7 percent) and fear of high fees (2 percent).

Many Americans "see themselves as savers, and they worry about capital preservation," Robert Stammers, director of investor education for the CFA Institute, told Bankrate. As a result, "they don't take the risk necessary to achieve the returns that they need to fulfill their long-term investment goals."

That's not good news for our retirement finances, of course. "The average person has less than $25,000 saved for retirement," Stammers said. "So people certainly aren't prepared, and that's just making them less prepared."

Adults younger than 30 are particularly underexposed to equities, with only 26 percent of them reporting they have stock investments. These people are missing out on the opportunity to compound their returns over a large number of years.

To be sure, given that the S&P 500 index has tripled in the last six years and now stands less than 2 percent from its record high, this might not be the best time to jump headlong into stocks.

When it comes to retirement, you're probably well aware of the need to orient your investments for your golden years, but you might be less aware of the need for an estate plan.

"I think that on a list of things to do, it's at the bottom, if it even makes the list," Nicole Hart, director of trusts and estates at Sontag Advisory, a financial planning firm, told USA Today retirement columnist Rodney Brooks.

He offers several pieces of advice for establishing an estate plan.

• Have both a financial planner and an estate lawyer look at every major financial document.
• "Make sure you have a health care proxy, living will and power of attorney. 'The possibility of getting sick is something everyone should be planning for,'" Carol Kroch, managing director of wealth planning at Wilmington Trust, told Brooks.
• While it may be uncomfortable, discuss all the estate issues with your family, so that when you do pass away, the inheritance outcome is clear to everyone.

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