The fund normally invests at least 80% of its net assets in the following types of U.S. dollar-denominated debt obligations: U.S. government and other public-sector entities, asset-backed and mortgage-backed obligations of U.S. and foreign issuers and corporate debt of U.S. and foreign issuers. It only invests in debt obligations rated investment-grade at the time of purchase by at least one major rating agency or, if unrated, determined by the advisor to be investment grade.