The iShares S&P U.S. Preferred Stock Index Fund (Ticker: PFF) seeks investment results that correspond generally to the performance, before fees and expenses, of the S&P U.S. Preferred Stock Index. The Index measures the performance of a select group of preferred stocks listed on the NYSE, AMEX and Nasdaq. The Index does not seek to directly reflect the performance of the companies issuing the preferred stock. The Index includes preferred stocks with a market capitalization over $100 million that meet minimum price, liquidity, maturity and other requirements and excludes preferred stock in company that are issued by special ventures (e.g., toll roads or dam operators) or structured products that are linked to indexes or other stocks. Preferred stock pays a specified dividend that must be paid before any dividends can be paid to common stockholders but generally do not carry voting rights and have economic characteristics similar to fixed-income securities. The index is calculated with a modified capitalization weighted scheme, with modifications being made to index shares to prevent single stock concentration (10% cap) and improve index liquidity. The index is rebalanced once a year, in September, when index shares and constituents are reviewed.