Strategy. The Fund seeks to track the investment results of the S&P U.S. Power Infrastructure Select Index (the Underlying Index ), which measures the performance of equity securities of U.S.-domiciled companies involved in U.S. power infrastructure, as determined by S&P Dow Jones Indices LLC (the Index Provider or SPDJI ). The Index Provider constructs the Underlying Index by including those companies within the S&P 1500 Composite Index (the Parent Index ) that derive at least 50% of their total revenue from U.S. power infrastructure-related businesses, excluding certain oil & gas companies not involved in natural gas, as defined by FactSets Revere Business Industry Classification System ( RBICS ). The Parent Index represents a broad measure of the investable U.S. equity market, … Show more… The Fund seeks to track the investment results of the S&P U.S. Power Infrastructure Select Index (the Underlying Index ), which measures the performance of equity securities of U.S.-domiciled companies involved in U.S. power infrastructure, as determined by S&P Dow Jones Indices LLC (the Index Provider or SPDJI ). The Index Provider constructs the Underlying Index by including those companies within the S&P 1500 Composite Index (the Parent Index ) that derive at least 50% of their total revenue from U.S. power infrastructure-related businesses, excluding certain oil & gas companies not involved in natural gas, as defined by FactSets Revere Business Industry Classification System ( RBICS ). The Parent Index represents a broad measure of the investable U.S. equity market, which typically covers approximately 90% of U.S. equity market capitalization and includes large-, mid- and small-capitalization companies. The U.S. power infrastructure-related businesses include the following sub-themes: (i) energy supply for electrification (ii) power generation, and (iii) power transmission, power distribution and storage which each include various RBICS groups of sub-industries. The Index Provider assigns each identified company to one of the sub-themes based on (1) the primary source of revenue or (2) other factors, including a companys business description, when the primary source of revenue is not definitive on a sub-theme. Constituents of the Underlying Index are weighted by float-adjusted market capitalization subject to a capping methodology at each quarterly rebalance. The capping methodology limits the weight of (1) any single company to a maximum of 6% of the Underlying Index, (2) all companies with a weight above 4.5% to an aggregate of 45% of the Underlying Index; (3) companies in the power generation sub-theme to 50% of the Underlying Index; and (4) companies in the energy supply for electrification and power transmission, power distribution, storage sub-themes to an aggregate of 50% of the Underlying Index. The Underlying Index is rebalanced quarterly and reconstituted annually in December. The Underlying Index includes large-, mid- and small-capitalization companies and may change over time. As of August 31, 2025, a significant portion of the Underlying Index is represented by securities of companies in the industrials and utilities industries or sectors. 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 capitalization and industry weightings), fundamental characteristics (such as return variability 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 generally will invest at least 80% of its assets in the component securities of its Underlying Index and in investments that have economic characteristics that are substantially identical to the component securities of its Underlying Index ( i.e ., depositary receipts representing securities of the Underlying Index) and may invest up to 20% of its assets in certain futures, options and swap contracts, cash and cash equivalents, including shares of money market funds advised by BFA or its affiliates, as well as in securities not 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 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 a product of SPDJI, 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) and repurchase agreements collateralized by U.S. government securities are not considered to be issued by members of any industry. Show less