DELISTED - The Fund seeks to track the investment results of the S&P AMT-Free Municipal Series 2015 IndexTM (the “Underlying Index”), which measures the performance of investment-grade, non-callable U.S. municipal bonds maturing in 2015. As of March 31, 2014, there were 2,939 issues in the Underlying Index.The Underlying Index includes municipal bonds primarily from issuers that are state or local governments or agencies such that the interest on the bonds is exempt from U.S. federal income taxes and the federal alternative minimum tax (“AMT”). Each bond must have a rating of at least BBB- by Standard & Poor's Ratings Services, Baa3 by Moody’s Investors Service, Inc. (“Moody's”), or BBB- by Fitch Ratings, Inc. and must have a minimum maturity par amount of $2 million to be eligible for inclusion in the Underlying Index. To remain in the Underlying Index, bonds must maintain a minimum par amount greater than or equal to $2 million as of each rebalancing date. All bonds in the Underlying Index will mature after May 31 and before September 2 of the year referenced in the name of the Underlying Index. When a bond matures in the Underlying Index, an amount representing its value at maturity will be included in the Underlying Index throughout the remaining life of the Underlying Index, and any such amount will be assumed to earn a rate equal to the performance of the Standard & Poor's Financial Services LLC's, a subsidiary of The McGraw-Hill Companies, Inc., Weekly High Grade Index, which consists of Moody's Investment Grade-1 municipal tax-exempt notes that are not subject to federal AMT. The Underlying Index is a market value weighted index and is rebalanced after the market close on the last business day of each month.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 keeping 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 the 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, duration, maturity or credit ratings and yield) and liquidity measures similar to those of the Underlying Index. The Fund may or may not hold all of the securities in the Underlying Index.The Fund generally invests at least 80% of its assets in the securities of its Underlying Index, except during the last months of the Fund's operations, as described below. The Fund may invest the remainder of its assets in cash and cash equivalents (including money market funds affiliated with BFA), as well as in municipal bonds not included in the Underlying Index, but which BFA believes will help the Fund track its Underlying Index. The Fund will generally hold municipal bond securities issued by state and local municipalities whose interest payments are exempt from U.S. federal income tax, the federal AMT and a federal Medicare contribution tax of 3.8% on “net investment income,” including dividends, interest and capital gains. In the last months of operation, as the bonds held by the Fund mature, the proceeds will not be reinvested in bonds but instead will be held in cash and cash equivalents, including, without limitation, money market funds affiliated with BFA, AMT-free tax-exempt municipal notes, variable rate demand notes and obligations, tender option bonds and municipal commercial paper. These cash equivalents may not be included in the Underlying Index. By September 1, 2015, the Underlying Index is expected to consist entirely of cash earned in this manner. Around the same time, the Fund will wind up and terminate, and its net assets will be distributed to then-current shareholders. 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 the collateral received).The Underlying Index is a product of an organization (the “Index Provider”) that 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. The Fund’s Index Provider is S&P Dow Jones Indices LLC, a subsidiary of McGraw Hill Financial, Inc. (“SPDJI”).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.
