A. Security Valuation: Securities are valued as of the close of trading on the New York Stock Exchange (generally 4 p.m., Eastern time) on the valuation date. Equity securities are valued at the latest quoted sales prices or official closing prices taken from the primary market in which each security trades; such securities not traded on the valuation date are valued at the mean of the latest quoted bid and asked prices. Bonds and other temporary cash investments are valued using the latest bid prices or using valuations based on a matrix system (which considers such factors as security prices, yields, maturities, and ratings), both as furnished by independent pricing services. Structured debt securities, including mortgages and asset-backed securities, are valued using the latest bid prices or using valuations based on a matrix system that considers such factors as issuer, tranche, nominal or option-adjusted spreads, weighted average coupon, weighted average maturity, credit enhancements, and collateral, as furnished by independent pricing services. Investments in Vanguard Market Liquidity Fund are valued at that fund's net asset value. Securities for which market quotations are not readily available, or whose values have been affected by events occurring before the fund’s pricing time but after the close of the securities’ primary markets, are valued by methods deemed by the valuation designee to represent fair value and subject to oversight by the board of trustees. These procedures include obtaining quotations from an independent pricing service, monitoring news to identify significant market- or security-specific events, and evaluating changes in the values of foreign market proxies (for example, ADRs, futures contracts, or exchange-traded funds), between the time the foreign markets close and the fund’s pricing time. When fair-value pricing is employed, the prices of securities used by a fund to calculate its net asset value may differ from quoted or published prices for the same securities.
B. Foreign Currency: Securities and other assets and liabilities denominated in foreign currencies are translated into U.S. dollars using exchange rates obtained from an independent third party as of the fund’s pricing time on the valuation date. Realized gains (losses) and unrealized appreciation (depreciation) on investment securities include the effects of changes in exchange rates since the securities were purchased, combined with the effects of changes in security prices. Fluctuations in the value of other assets and liabilities resulting from changes in exchange rates are recorded as unrealized foreign currency gains (losses) until the assets or liabilities are settled in cash, at which time they are recorded as realized foreign currency gains (losses).
C. To Be Announced (TBA) Transactions: A TBA transaction is an agreement to buy or sell mortgage-backed securities with agreed-upon characteristics (face amount, coupon, maturity) for settlement at a future date. The fund may be a seller of TBA transactions to reduce its exposure to the mortgage-backed securities market or in order to sell mortgage-backed securities it owns under delayed-delivery arrangements. When the fund is a buyer of TBA transactions, it maintains cash, short-term investments, or Treasuries in an amount sufficient to meet the purchase price at the settlement date of the TBA transaction. The primary risk associated with TBA transactions is that a counterparty may default on its obligations. The fund mitigates its counterparty risk by, among other things, performing a credit analysis of counterparties, allocating transactions among numerous counterparties, and monitoring its exposure to each counterparty. The fund may also enter into a Master Securities Forward Transaction Agreement (MSFTA) with certain counterparties and require them to transfer collateral as security for their performance. In the absence of a default, the collateral pledged or received by the fund cannot be repledged, resold, or rehypothecated. Under an MSFTA, upon a counterparty default (including bankruptcy), the fund may terminate any TBA transactions with that counterparty, determine the net amount owed by either party in accordance with its MSFTA, and sell or retain any collateral held up to the net amount owed to the fund under the MSFTA.
D. Mortgage Dollar Rolls: The fund enters into mortgage-dollar-roll transactions, in which the fund sells mortgage-backed securities to a dealer and simultaneously agrees to purchase substantially similar securities in the future at a predetermined price on a predetermined date. The fund forgoes principal and interest paid on the securities sold. In exchange for the forgone principal and interest paid, the fund is compensated by investing the proceeds of the sale, typically in high-quality short-term fixed income securities, and earning interest on such investments. Further the fund receives a lower price on the securities to be repurchased. The fund also enters into mortgage-dollar-roll transactions in which the fund buys mortgage-backed securities from a dealer pursuant to a TBA transaction and simultaneously agrees to sell substantially similar securities in the future at a predetermined price. The securities bought in mortgage-dollar-roll transactions are used to cover an open TBA sell position. The fund continues to earn interest on mortgage-backed security pools already held and receives a lower price on the securities to be sold in the future. The fund accounts for mortgage-dollar-roll transactions as purchases and sales; as such, these transactions may increase the fund’s portfolio turnover rate. Amounts to be received or paid in connection with open mortgage dollar rolls are included in Receivables for Investment Securities Sold or Payables for Investment Securities Purchased.
E. Futures Contracts: The fund uses futures contracts to invest in fixed income asset classes with greater efficiency and lower cost than is possible through direct investment, to add value when these instruments are attractively priced, or to adjust sensitivity to changes in interest rates. The primary risks associated with the use of futures contracts are imperfect correlation between changes in market values of bonds held by the fund and the prices of futures contracts, and the possibility of an illiquid market. Counterparty risk involving futures is mitigated because a regulated clearinghouse is the counterparty instead of the clearing broker. To further mitigate counterparty risk, the fund trades futures contracts on an exchange, monitors the financial strength of its clearing brokers and clearinghouse, and has entered into clearing agreements with its clearing brokers. The clearinghouse imposes initial margin requirements to secure the fund’s performance and requires daily settlement of variation margin representing changes in the market value of each contract. Any securities pledged as initial margin for open contracts are noted in the Schedule of Investments.
Futures contracts are valued at their quoted daily settlement prices. Fluctuations in the value of the contracts are recorded as an asset (liability).
F. Forward Currency Contracts: The fund enters into forward currency contracts to protect the value of securities and related receivables and payables against changes in future foreign exchange rates. Risks associated with these types of forward currency contracts include movement in the values of the foreign currencies relative to the U.S. dollar and the ability of the counterparties to fulfill their obligations under the contracts. The fund mitigates its counterparty risk by entering into forward currency contracts only with a diverse group of prequalified counterparties, monitoring their financial strength, entering into master netting arrangements with its counterparties, and requiring its counterparties to transfer collateral as security for their performance. In the absence of a default, the collateral pledged or received by the fund cannot be repledged, resold, or rehypothecated. The master netting arrangements provide that, in the event of a counterparty’s default (including bankruptcy), the fund may terminate the forward currency contracts, determine the net amount owed by either party in accordance with its master netting arrangements, and sell or retain any collateral held up to the net amount owed to the fund under the master netting arrangements. The forward currency contracts contain provisions whereby a counterparty may terminate open contracts if the fund’s net assets decline below a certain level, triggering a payment by the fund if the fund is in a net liability position at
