A computer-implemented apparatus is provided for administering an actively managed investment company that invests assets in fixed income securities. The apparatus includes an investment company processor, an investment company portfolio trading and managing computer, and a computer database. The investment company processor issues one or more classes of shares that are listed for trading on a securities exchange and that are bought and sold in a secondary market at negotiated market prices. The investment company portfolio trading and managing computer receives instructions to select and hold a portfolio of fixed income securities that relate to a benchmark index. The selection is made in an actively managed manner such that the duration range of the securities holdings is either longer than the duration of the benchmark index, close to the duration of the benchmark index, or shorter than the duration of the benchmark index. The investment company portfolio trading and managing computer also defines a creation unit basket having a duration that is equal to a midpoint of the duration range of the securities holdings of the investment company that are held in the investment company portfolio trading and managing computer. The computer database stores the creation unit basket.