It's been a tough decade for stock funds

— -- For some investors, the lost decade in stocks is more like the dead decade.

The average diversified U.S. stock fund gained just 13% from 1998 through 2008, according to Lipper, which tracks the funds. But more than a dozen of 1998's largest and most popular funds lost 30% or more.

But it's unusual for large funds to post such big long-term losses. Mutual fund companies profit by collecting fees on a fund's assets, and it's tough to persuade investors to buy a fund with a lousy long-term record. Fund companies often go to great lengths to make sure that their funds rack up decent long-term records. What happened with these funds?

•A rotten market. The current bear market, as well as the 2000-02 bear market, are among the most savage since the Great Depression. The Standard & Poor's 500-stock index has fallen 13% the past decade, including reinvested dividends, so even good managers have struggled.

•Out-of-favor investment styles. Some of the funds with the worst long-term records are large-company growth funds. These funds look for stocks of companies with soaring earnings. It was a great approach in the 1990s, when large-cap growth trounced every other investment style. Starting in 2000, however, technology stocks and other growth segments have far underperformed the S&P 500. The technology-laden Nasdaq stock index has fallen 39% the past decade.

•Spotty management. Some fund companies had managers with great records who went through a bad patch.