The Fund seeks to track the investment results of the S&P International Preferred Stock IndexTM (the “Underlying Index”), which measures the performance of a select group of preferred stocks traded on non-U.S. developed market exchanges as defined by S&P Dow Jones Indices LLC (the “Index Provider” or “SPDJI”), a subsidiary of S&P Global, Inc. Securities listed in emerging markets are excluded. The Underlying Index includes developed-market preferred stocks with full market capitalization of at least $125 million ($100 million for current constituents) that meet minimum liquidity, trading volume, maturity and other requirements determined by the Index Provider. The Underlying Index excludes certain issues of preferred stock, such as those that are issued by special ventures (e.g., toll roads or dam operators) or structured products that are linked to indices or other stocks. In general, preferred stock is a class of equity security that pays a specified dividend that must be paid before any dividends can be paid to common stockholders and takes precedence over common stock in the event of a company’s liquidation. Although preferred stocks represent a partial ownership interest in a company, preferred stocks generally do not carry voting rights and have economic characteristics similar to fixed-income securities. Preferred stocks generally are issued with a fixed par value and pay dividends based on a percentage of that par value at a fixed or variable rate. Additionally, preferred stocks often have a liquidation value that generally equals the original purchase price of the preferred stock at the date of issuance. The Underlying Index may include many different categories of preferred stock, such as floating, variable and fixed-rate preferreds, callable preferreds, convertible preferreds, cumulative and non-cumulative preferreds or various other traditional and hybrid issues of preferred stock. As of March 31, 2021, the Underlying Index was comprised of securities of companies in the following countries: Canada, Singapore, Sweden and the United Kingdom (the “U.K.”). The Underlying Index will include large-, mid- and small-capitalization companies and may change over time. As of March 31, 2021, a significant portion of the Underlying Index is represented by securities of companies in the energy and financials industries or sectors. The components of the Underlying Index are likely to change over time. BFA uses a “passive” or indexing approach to try to achieve the Fund’s investment objective. Unlike many investment companies, 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 that collectively has an investment profile similar to that of an applicable underlying index. The securities 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 securities in 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 investments not 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.