To pursue its goal, the fund generally invests in securities that are included in the Bloomberg US Treasury 3-10 Year Index. The index includes all publicly-issued U.S. Treasury securities that have a remaining maturity of greater than or equal to three years and less than ten years, are rated investment grade, and have dollar 300 million or more of outstanding face value. The securities in the index must be denominated in U.S. dollars and must be fixed-rate and non-convertible. The index excludes U.S. Treasury stripped securities. The index is market capitalization weighted and the securities in the index are updated on the last business day of each month. It is the funds policy that under normal circumstances it will invest at least 90 percent of its net assets (including, for this purpose, any borrowings for investment purposes) in securities included in the index. The fund will notify its shareholders at least 60 days before changing this policy.