Under normal market conditions, the fund invests at least 80% of its net assets (plus any borrowings for investment purposes) in mortgage-backed securities. The fund may invest in mortgage-related securities issued or guaranteed by U.S. governmental entities and privately issued mortgage-related securities. These may include residential mortgage-backed securities, commercial mortgage-backed securities and to-be-announced mortgage contracts, and may be rated investment grade or below. Investment-grade securities are rated from AAA to BBB- by Standard & Poors Ratings Services (S&P) or by Fitch Ratings (Fitch) or from Aaa to Baa3 by Moodys Investors Service, Inc. (Moodys), or comparable rating by any nationally recognized statistical rating organization (NRSRO), or their unrated equivalents. Below investment-grade securities are rated BB and below by S&P or Fitch or Ba and below by Moodys, or comparable rating by any NRSRO, or their unrated equivalents. The fund will limit its investment in below investment grade securities to 20% of its net assets at time of purchase. The funds investment policies are based on credit ratings at the time of purchase. There is no limit on the funds average maturity.