Heed the warning label on mutual funds — passive is better

The warning is posted in fine print at the bottom of all mutual fund advertisements: "Past performance does not guarantee future results."

But when it comes to actively managed mutual funds, that warning should perhaps be updated to: "Strong performance almost certainly guarantees worse performance in the future."

Such a caveat would simply reflect what the data tell us about actively managed funds, which are managed by a person or team instead of being "passively" pegged to an index or other benchmark. It also explains why retirement investors have been shoveling billions of dollars into passive total-market index funds and exchange-traded funds.

The latest nail in the coffin for active funds comes from S&P Dow Jones Indices, which this month released a semiannual scorecard that tracks consistency of top-performing mutual funds over time. The study concludes that very few equity funds consistently stay at the top, especially after five or more years.

Specifically: Only 7.3 percent of domestic equity funds that were in the top quartile of performance in March 2014 were still there two years later.

Only 3.7 percent of large-cap funds maintained top-half performance over five consecutive 12-month periods. For mid-cap funds, the comparable figure was 5.8 percent; and 7.8 percent for small-cap funds.

The lion's share of retirement dollars is going into passive funds these days — and investors are better off for it. Separate research by S&P Dow Jones finds 76.2 percent of retail mutual fund managers underperformed the S&P 500 over the past five years.

Another striking statistic in the S&P Dow Jones report is that about one-third of equity funds in the fourth quartile were liquidated or merged over the last five years.

Investors get it. Ten years ago, 20 percent of net assets in U.S. mutual funds were in passive vehicles, according to Morningstar. At the end of 2015, that figure surpassed 40 percent for the first time.

S&P Dow Jones reports that a couple of active fund categories — mortgage-backed securities and general municipal debt funds — have been able to stay in the top quartile over the past five years.

But on the equity side, the message is clear, according to Soe. "The average investor is almost always better off with passive options."