Morningstar rates thousands of funds a year, and at least during 2018, several big funds had changes that caused Morningstar to upgrade them, according to a write-up by Russell Kinnel, the firm's director of manager research. Here are some of the largest funds and what induced the upgrade:
Pimco Total Return (PTTRX): The loss of Bill Gross in 2014 — and along with him, many redemptions — caused Morningstar to reduce the fund at that time to a bronze rating. But this year the firm moved them to gold from silver as they found that not only did the outflows not affect performance, "a credit to the fund's design and its trading desk," the fund actually has "outperformed peers and benchmark since Gross' departure."
Fidelity Extended Market Index (FSEVX): Cost matters, and in this case Fidelity's launch of zero-cost funds helped established index funds, Morningstar notes. By lowering fees across the board and eliminating minimums, FSEVX is just five basis points, which is a key reason why Morningstar upped its ranking to gold from silver.