The investment seeks to track the performance of a market-weighted Treasury index with a long-term dollar-weighted average maturity. The fund employs an indexing investment approach designed to track the performance of the Bloomberg Barclays U.S. Long Treasury Bond Index. This index includes fixed income securities issued by the U.S. Treasury (not including inflation-protected bonds), with maturities greater than 10 years. Under normal circumstances, at least 80% of the fund's assets will be invested in bonds included in the index.