Over the past year and for periods of five, 10, 20 and 30 years, the average mutual fund investor has underperformed the markets for both stocks and bonds, according to research firm Dalbar.

The Dalbar data leads to the inescapable conclusion that most investors are really terrible at investing. They panic and sell at the wrong moments, hurting their chances of success.

The shocking reality is that investors actually made themselves poorer by giving in to their whims. Just look at the Dalbar results for 2018. The inflation rate was 1.93 percent, which means that investors would have had to earn that just amount to tread water. Instead, the average stock fund investor lost 9.42 percent, for a gap of more than 11 percentage points!

Consider a few more dismal data points for stock mutual fund investors. Compared with the S&P 500, through Dec. 31, 2018, those investors underperformed by:

— 5.88 percentage points, annualized, over 30 years;
— 3.46 percentage points, annualized, over 10 years;
— 4.35 percentage points, annualized over 5 years.

The lesson investors can learn from this research is the value of staying the course and not making any sudden moves. According to Dalbar president Louis Harvey, “If you are going to need money soon, for retirement or to finance education or to buy a house, you shouldn’t take risks with it. Keep that money safe and separate. But for the rest of your money, the long-term money, stay invested in the market. Don’t do anything fancy with it, and just keep it there.”

Wise words to remember the next time markets start getting jittery.