The fund will invest at least 80% of its assets in the component securities of the underlying index, and the fund will invest at least 90% of its assets in fixed income securities of the types included in the underlying index that BFA believes will help the fund track the underlying index. The underlying index is a subset of the Bloomberg U.S. Corporate Index, which measures the performance of the Aaa - A rated range of the fixed-rate, U.S. dollar-denominated taxable, corporate bond market.