To pursue its goal, the fund normally invests substantially all, but at least 80 percentage of its assets in bonds comprising the Bloomberg Barclays US Aggregate Total Return Index and TBA transactions (as defined below) representing bonds included in the index. The Bloomberg Barclays US Aggregate Total Return Index is designed to measure the investment grade, U.S. dollar-denominated, fixed-rate taxable bond market. The index includes Treasuries, government-related and corporate securities, mortgage-backed pass-through securities (agency fixed-rate), commercial mortgage-backed securities (agency and non-agency) and other asset-backed securities having at least one year until final maturity.