CHICAGO (AP) ¿ Morningstar Inc. said Wednesday it is launching ratings and detailed reports on target-date funds. The style of mutual funds have been criticized for losing significant value as the stock market deteriorated last year even though they were sold as safe investments for retirement.

The average 2010 target-date fund, for example, lost 25 percent last year, said John Rekenthaler, vice president of research for Morningstar.

The funds are designed to align investment risk with the year an investor plans to retire. As the investor approaches retirement, the funds are designed to shift from stocks to less risky bonds or other investments.

The top performing 2010 fund lost just 3.6 percent last year, while the worst was down 41 percent, he said, illustrating the wide variance in investment strategies used.

"Surprise about these variations in performance reveals the lack of knowledge about this new, fast-growing category of mutual funds," he said.

Rekenthaler said the new research and reports will help inform investors about the funds, which have become the default investment in many employer offered 401(k) plans.

Reports on 20 fund families will begin in the third quarter of this year, he said.

The reports will evaluate the fund managers, the parent company offering the fund, performance, the fund's holdings and its price.

The reviews will be updated annually.

Morningstar, an independent investment research company, announced the new reports at its annual investor conference under way in Chicago, where the company is based.

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