Strategy. The Fund seeks to track the investment results of the Bloomberg U.S. Total Fixed Income Market Index (the Underlying Index ), which measures the performance of U.S. dollar-denominated fixed income securities that are rated either investment-grade or high yield (as determined by Bloomberg Index Services Limited (the Index Provider or Bloomberg )). The Underlying Index includes fixed and floating rate U.S. Treasury bonds, U.S. Treasury Inflation-Protected Securities ( TIPS ), government-related bonds, investment-grade and high yield U.S. corporate bonds, securitized assets, fixed and floating rate notes and corporate bonds, leveraged loans, Eurodollar bonds, bonds registered with the SEC or exempt from registration at the time of issuance or offered pursuant to Rule 144A with or without registration rights and U.S. … Show more… The Fund seeks to track the investment results of the Bloomberg U.S. Total Fixed Income Market Index (the Underlying Index ), which measures the performance of U.S. dollar-denominated fixed income securities that are rated either investment-grade or high yield (as determined by Bloomberg Index Services Limited (the Index Provider or Bloomberg )). The Underlying Index includes fixed and floating rate U.S. Treasury bonds, U.S. Treasury Inflation-Protected Securities ( TIPS ), government-related bonds, investment-grade and high yield U.S. corporate bonds, securitized assets, fixed and floating rate notes and corporate bonds, leveraged loans, Eurodollar bonds, bonds registered with the SEC or exempt from registration at the time of issuance or offered pursuant to Rule 144A with or without registration rights and U.S. dollar- denominated emerging market bonds. The securities in the Underlying Index must be denominated in U.S. dollars. The Underlying Index consisted of securities from 108 countries or regions as of October 31, 2025. As of October 31, 2025, a significant portion of the Underlying Index is represented by U.S. agency mortgage-backed securities and U.S. Treasury bonds. The components of the Underlying Index are likely to change over time. BFA uses an indexing approach to try to achieve the Funds investment objective. The Fund does not try to beat the index it tracks and does not seek temporary defensive positions when markets decline or appear overvalued. Indexing may eliminate the chance that the Fund will substantially outperform the Underlying Index but also may reduce some of the risks of active management, such as poor security selection. Indexing seeks to achieve lower costs and better after-tax performance by aiming to keep portfolio turnover low in comparison to actively managed investment companies. BFA uses a representative sampling indexing strategy to manage the Fund. Representative sampling is an indexing strategy that involves investing in a representative sample of securities or other instruments that collectively has an investment profile similar to that of an applicable underlying index. The instruments selected are expected to have, in the aggregate, investment characteristics (based on factors such as market value and industry weightings), fundamental characteristics (such as return variability, duration ( i.e. , an instrument's price sensitivity to a change in interest rates), maturity or credit ratings and yield) and liquidity measures similar to those of an applicable underlying index. The Fund may or may not hold all of the components of the Underlying Index. The Fund will invest at least 80% of its assets in the component securities of the Underlying Index and to-be-announced transactions ( TBAs ) that have economic characteristics that are substantially identical to the economic characteristics of 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 Fund will invest no more than 10% of its assets in futures, options and swaps contracts that BFA believes will help the Fund track the Underlying Index as well as in fixed income securities other than the types included in the Underlying Index, but which BFA believes will help the Fund track the Underlying Index. Cash and cash equivalent investments associated with a TBA position will be treated as part of that position for purposes of calculating investments in the component securities of the Underlying Index. Cash and cash equivalent investments associated with a derivative position will be treated as part of that position for the purposes of calculating the percentage of investments included in the Underlying Index. The Fund seeks to track the investment results of the Underlying Index before fees and expenses of the Fund. The Fund may lend securities representing up to one-third of the value of the Fund's total assets (including the value of any collateral received). The Underlying Index is sponsored by Bloomberg, which is ? independent of the Fund and BFA. The Index Provider determines the composition and relative weightings of the securities in the Underlying Index and publishes information regarding the market value of the Underlying Index. Industry Concentration Policy. The Fund will concentrate its investments ( i.e. , hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. For purposes of this limitation, securities of the U.S. government (including its agencies and instrumentalities), repurchase agreements collateralized by U.S. government securities, and securities of state or municipal governments and their political subdivisions are not considered to be issued by members of any industry. Show less