Bad market timing and poor stock picking kept most investors from fully reaping the gains of the bull market last year.
"The average investor held too much in cash, was too concentrated in stocks that didn't perform well and avoided financial stocks that rallied last year," said Hart Lambur, co-founder and CEO of Openfolio, a social network with more than 70,000 members who share their investment portfolios.
The average investor on Openfolio had a gain of roughly 5 percent in 2016. That lagged the nearly 12 percent total return of the S&P 500, which includes dividends, by more than 7 percentage points last year. (See chart below.)