The fund invests at least 80% of its net assets (including the amount of any borrowings for investment purposes) in bonds, including debt instruments issued by the U.S. government and its agencies, debt securities issued by corporations, mortgage- and other asset-backed securities, and dollar-denominated securities issued by foreign governments, companies or other entities. The fund also invests at least 65% of its total assets in securities that, at the time of purchase, are rated investment grade or are unrated but determined to be of comparable quality.