NEW YORK (MainStreet) — Investors aim to earn a return of 9.8% above the rate of inflation. Considering an average annual rate of inflation topping 4.2% since 1964, that would mean a required rate of return of nearly 14%. However, the S&P 500 has seen an average gain of just 10% over the past 50 years.

So how do investors expect to earn such a return? Certainly not by adding additional risk, according to a survey fielded by Natixis Global Asset Management. Americans are willing to take only a minimal amount of risk in order to meet their investment goals of retirement income, housing and healthcare expenses. It's a mathematical equation that simply doesn't add up.

"Many investors have set aggressive investment targets, but don't have a realistic way of reaching them," says John Hailer, CEO of Natixis Global Asset Management. "Something has to change. The markets have reached new heights and investors feel generally comfortable about portfolio performance. But without a plan that incorporates individual risk and personal benchmarks, the odds are diminished that investors' will meet their goals."

The survey included 1,050 investors across the U.S. as part of a global poll of nearly 6,000 investors in 14 countries. And despite strengthening global markets many investors remain fearful of losses.

Seven in ten (71%) of investors surveyed said asset growth is increasingly a priority over principal protection, yet 56% say they are only willing to take minimal risk to achieve high returns. Three-quarters (76%) of investors only own investments they understand well – yet just one-quarter feel their overall investment knowledge is very strong. When making investment decisions, more than three-quarters (79%) of investors say they simply follow their gut instinct.

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"50% have no clear investment goals and 54% have no financial plan, so it's not surprising that when asked how they define investing success – some look at asset levels and others look at comfort level – rather than meeting long-term financial goals," says Hailer.

Every financial advisor should file this statistic away for future use: 84% of investors say they would be happy to achieve their long-term investment goals, even if they underperformed the market in a given year. In fact, more than two-thirds (69%) said they would be happy to achieve 10% returns even if the overall market gained 25%.

As Americans see an increase in life expectancies, they face funding a retirement that could span more than two decades – however, only 27% are very confident that their current investment strategy will deliver such a long-term stable income. The biggest concern is the uninsured cost of long-term care in old age, which more than half (53%) of investors admit is the biggest risk to financial security in retirement.

--Written by Hal M. Bundrick for MainStreet