Primary Risks
An investment in the Fund could lose money over short or even long periods. You should expect the Fund’s share price and total return to fluctuate within a wide range, like the fluctuations of the overall bond market. The Fund is subject to the following risks, which could affect the Fund’s performance:
•
Prepayment risk,
which is the chance that during periods of falling interest rates, homeowners will refinance their mortgages before their maturity dates, resulting in prepayment of mortgage-backed securities held by the Fund. The Fund would then lose any price appreciation above the mortgage’s principal and would be forced to reinvest the unanticipated proceeds at lower interest rates, resulting in a decline in the Fund’s income. Prepayment risk, which is a type of call risk, is high for the Fund.
•
Interest rate risk
, which is the chance that bond prices overall will decline because of rising interest rates. In addition, when interest rates decline, mortgage-backed securities’ prices typically do not rise as much as the prices of comparable bonds. This is because the market tends to discount mortgage-backed securities’ prices for prepayment risk when interest rates decline. Interest rate risk should be moderate for the Fund.
•
Income risk
, which is the chance that the Fund’s income will decline because of falling interest rates. Income risk is generally moderate for intermediate-term bond funds, so investors should expect the Fund’s monthly income to fluctuate accordingly.
•
Credit risk,
which is the chance that the issuer of a mortgage-backed security will fail to pay interest and principal in a timely manner, or that negative perceptions of the issuer’s ability to make such payments will cause the price of that bond to decline. Credit risk should be very low for the Fund because it invests in securities issued by U.S. government agencies and instrumentalities, including many securities backed by the full faith and credit of the U.S. government.
•
Index sampling risk,
which is the chance that the securities selected for the Fund, in the aggregate, will not provide investment performance matching that of the Fund’s target index. Index sampling risk for the Fund should be low.
Because ETF Shares are traded on an exchange, they are subject to additional risks:
• The Fund’s ETF Shares are listed for trading on Nasdaq and are bought and sold on the secondary market at market prices. Although it is expected that the market price of an ETF Share typically will approximate its net asset value (NAV), there may be times when the market price and the NAV differ significantly. Thus, you may pay more or less than NAV when you buy ETF Shares on the secondary market, and you may receive more or less than NAV when you sell those shares.
• Although the Fund’s ETF Shares are listed for trading on Nasdaq, it is possible that an active trading market may not be maintained.
3
• Trading of the Fund’s ETF Shares on Nasdaq may be halted by the activation of individual or marketwide “circuit breakers” (which halt trading for a specific period of time when the price of a particular security or overall market prices decline by a specified percentage). Trading of the Fund’s ETF Shares may also be halted if (1) the shares are delisted from Nasdaq without first being listed on another exchange or (2) Nasdaq officials determine that such action is appropriate in the interest of a fair and orderly market or for the protection of investors.
An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Annual Total Returns
The following bar chart and table are intended to help you understand the risks of investing in the Fund. The bar chart shows how the performance of the Fund‘s ETF Shares (based on NAV) has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the ETF Shares compare with those of the Fund‘s target index, which has investment characteristics similar to those of the Fund. Keep in mind that the Fund’s past performance (before and after taxes) does not indicate how the Fund will perform in the future. Updated performance information is available on our website at
vanguard.com/performance
or by calling Vanguard toll-free at 800-662-7447.
Annual Total Returns — Vanguard Mortgage-Backed Securities Index Fund ETF Shares
1
1 The year-to-date return as of the most recent calendar quarter, which ended on September 30, 2013, was –0.86%.
During the periods shown in the bar chart, the highest return for a calendar quarter was 2.73% (quarter ended June 30, 2010), and the lowest return for a quarter was –0.44% (quarter ended December 31, 2012).
4