To pursue its goal, the fund generally invests in securities that are included in the index. The index includes all publicly issued, U.S. Treasury securities that have a remaining maturity of ten or more years, are rated investment grade, and have $300 million or more of outstanding face value. It is the fund's policy that under normal circumstances it will invest at least 90% of its net assets (including, for this purpose, any borrowings for investment purposes) in securities included in the index.