Morningstar rates investments from one to five stars based on how well they've performed in comparison to similar investments, after adjusting for risk and accounting for all relevant sales charges. Within each Morningstar Category, the top 10% of investments receive five stars, the next 22.5% four stars, the middle 35% three stars, the next 22.5% two stars, and the bottom 10% receive one star. Investments are rated for up to three time periods - 3, 5, and 10 years, and these ratings are combined to produce an overall rating. Investments with less than three years of history are not rated. Ratings are objective, based entirely on a mathematical evaluation of past performance. They're a useful tool for identifying investments worthy of further research, but shouldn't be considered buy or sell recommendations.
For additional information, please see: Morningstar Fund Rating Methodology
