While the investment objective stated in a fund's prospectus may or may not reflect how the fund actually invests, the Morningstar category is assigned based on the underlying securities in each portfolio.
Morningstar categories help investors and investment professionals make meaningful comparisons between funds. The categories make it easier to build well-diversified portfolios, assess potential risk, and identify top-performing funds. We place funds in a given category based on their portfolio statistics and compositions over the past three years.
If the fund is new and has no portfolio history, we estimate where it will fall before giving it a more permanent category assignment. When necessary, we may change a category assignment based on recent changes to the portfolio.
In order to make sure Morningstar categories reflect the latest developments in the fund space, Morningstar reviews and updates the definitions of Morningstar categories regularly.
Please find the latest version (as of April 2019) of Morningstar Category Definitions.