“They paid too much attention to the fear du jour,” Jeffrey Saut, chief investment strategist at Raymond James & Associates, said in the Bloomberg article.

“There has been an overriding theme of anxiety among investors about the stock market,” Avi Nachmany, director of research at Strategic Insight, said in the WSJ story. “Those companies whose total focus on stocks are suffering.”

According to Morningstar data, U.S. large growth stock mutual funds returned an average 15.3% over 2012, whereas similar ETF products garnered 16.4%.

“ETFs have really won people over,” Deborah Fuhr, a partner at ETFGI LLP, said in the WSJ report.

For more information on ETFs, visit our ETF 101 category.

Max Chen contributed to this article.