It's tempting to look at which mutual funds did best in 2015 and just invest in those. Winners win, right?

Not in the investing world. It's tough for funds to

stay on top, and last year's winners regularly turn into this year's losers.

Look at what happened to the handful of index and actively managed mutual funds that returned 40 percent or more in 2014. Their returns towered over the 14 percent that a Standard & Poor's 500 index fund produced.

But seven of the 10 went on to lose money the following year. You would have had a slightly better chance of making money in 2015 by picking a fund at random.

The figures dovetail with a raft of studies that suggest investors should consider much more than just past performance when choosing funds.

It turns out that even when funds perform well over long periods, compared with similar funds, it doesn't mean they will continue to do so.

A study released by Morningstar last week looked at fund returns in 14 categories, going back to 1996. It identified which high-yield bond funds were in the top 20 percent for the five years through 2001, then checked to see how they performed over the ensuing five years against the funds that had been in the bottom 20 percent.

The researchers found only small differences in ensuing success for the top and bottom funds in most categories, as long as the time frame was longer than a year.


"Even the best managers generally do not consistently outperform," the researchers wrote in their report. "Those who lack the patience to stick with an active manager through multiyear rough patches may be better off in a low-cost index fund."

S&P Dow Jones Indices, meanwhile, keeps its own scorecard of how many mutual-fund managers are able to stay in the top quartile or even top half of their categories. Its verdict: very few.

Of the 539 funds that ranked in the top half of large-company funds in the year through March 2011, 52 percent repeated the feat the following year. That's only slightly better than a coin flip.

The difficulty fund managers have in staying on top serves as a reminder to resist the temptation to hop from one fad to another. Investors are notorious for chasing after whatever's performing well and fleeing whatever's struggling.

The largest actively managed stock fund, American Funds' Growth Fund of America, returned an annualized 7.2 percent over the decade through 2015, for example.

That's how much investors would have made if they bought at the start of that decade and simply held it. But most investors didn't do that. Instead, many bought more shares when performance was good and sold when performance lagged. That means the average investor in the fund got a 5.3 percent annual return over the decade, Morningstar reported.

Investors also should look to keep their fund expenses low. A fund with high fees has to perform much better just to match the performance of a low-fee fund.

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