Dec. 22, 2020
Institutional \| Vanguard Extended Duration Treasury Index Fund
<span style="color:#000000;font-family:Arial;font-size:13pt;font-weight:bold;margin-left:0%;">Fund Summary</span>
<span style="color:#000000;font-family:Arial;font-size:10pt;font-weight:bold;margin-left:0%;">Investment Objective</span>
The Fund seeks to track the performance of an index of extended-duration zero-coupon U.S. Treasury securities.
<span style="color:#000000;font-family:Arial;font-size:10pt;font-weight:bold;margin-left:0%;">Fees and Expenses</span>
The following table describes the fees and expenses you may pay if you buy, hold, and sell Institutional Shares or Institutional Plus Shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the table and example below.
<span style="color:#000000;font-family:Arial;font-size:8.5pt;font-weight:bold;margin-left:0%;">Shareholder Fees</span><span style="color:#000000;font-family:Arial;font-size:8.5pt;">(Fees paid directly from your investment)</span>
<span style="color:#000000;font-family:Arial;font-size:8.5pt;font-weight:bold;margin-left:0%;">Annual Fund Operating Expenses</span><span style="color:#000000;font-family:Arial;font-size:8.5pt;">(Expenses that you pay each year as a percentage of the value of your investment)</span>
<span style="color:#000000;font-family:Arial;font-size:9.5pt;margin-left:0%;">Examples</span>
The following examples are intended to help you compare the cost of investing in the Fund’s Institutional Shares or Institutional Plus Shares with the cost of investing in other mutual funds. They illustrate the hypothetical expenses that you would incur over various periods if you were to invest $10,000 in the Fund's shares. These examples assume that the shares provide a return of 5% each year and that total annual fund operating expenses remain as stated in the preceding table. You would incur these hypothetical expenses whether or not you were to redeem your investment at the end of the given period. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
<span style="color:#000000;font-family:Arial;font-size:9.5pt;margin-left:0%;">Portfolio Turnover</span>
The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in more taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the previous expense examples, reduce the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 17% of the average value of its portfolio.
<span style="color:#000000;font-family:Arial;font-size:10pt;font-weight:bold;margin-left:0%;">Principal Investment Strategies</span>
The Fund employs an indexing investment approach designed to track the performance of the Bloomberg Barclays U.S. Treasury STRIPS 20–30 Year Equal Par Bond Index. This Index includes zero-coupon U.S. Treasury securities (Treasury STRIPS), which are backed by the full faith and credit of the U.S. government, with maturities ranging from 20 to 30 years. A Treasury STRIP represents a single coupon payment, or a single principal payment, from a U.S. Treasury security that has been “stripped” into separately tradable components.The Fund invests by sampling the Index, meaning that it holds a range of securities that, in the aggregate, approximates the full Index in terms of key risk factors, including duration, cash flow, and other characteristics. All of the Fund’s investments will be selected through the sampling process and, under normal circumstances, at least 80% of the Fund’s assets will be invested in U.S. Treasury securities held in the Index. The Fund maintains a dollar-weighted average maturity consistent with that of the Index. As of August 31, 2020, the dollar-weighted average maturity of the Index was 24.7 years.
<span style="color:#000000;font-family:Arial;font-size:10pt;font-weight:bold;margin-left:0%;">Principal Risks</span>
An investment in the Fund could lose money over short or long periods of time.You should expect the Fund's share price and total return to fluctuate within a wide range. The Fund is subject to the following risks, which could affect the Fund's performance, and the level of risk may vary based on market conditions:• Interest rate risk , which is the chance that bond prices overall will decline because of rising interest rates. The prices of long-term bonds, such as those held by the Fund, are much more sensitive to interest rate changes than are the prices of short-term bonds. Interest rate risk is expected to be very high for the Fund because it invests primarily in zero-coupon long-term bonds, which have prices that are even more sensitive to interest rate changes than are coupon-bearing bonds of similar maturity. Because the Fund invests primarily in Treasury STRIPS with maturities ranging from 20 to 30 years, rising interest rates may cause the value of the Fund’s investments to decline significantly.• 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 is expected to be low.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.
<span style="color:#000000;font-family:Arial;font-size:10pt;font-weight:bold;margin-left:0%;">Annual Total Returns</span>
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 Institutional Shares (including annual fund operating expenses but excluding shareholder fees) has varied from one calendar year to another over the periods shown. If applicable shareholder fees were reflected, returns would be less than those shown in the bar chart. The table shows how the average annual total returns of the share classes presented (including annual fund operating expenses and any applicable shareholder fees) compare with those of the Fund's target index and another comparative index, which have 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.
<span style="color:#000000;font-family:Arial;font-size:8pt;font-weight:bold;">Annual Total Returns — Vanguard Extended Duration Treasury Index Fund Institutional Shares</span><span style="color:#000000;font-family:Arial;font-size:5pt;font-weight:bold;position:relative;top:-3.25pt;">1</span>
During the periods shown in the bar chart, the highest and lowest returns for a calendar quarter were:
<span style="color:#000000;font-family:Arial;font-size:8.5pt;font-weight:bold;">Average Annual Total Returns for Periods Ended December 31, 2019</span>
Actual after-tax returns depend on your tax situation and may differ from those shown in the preceding table. When after-tax returns are calculated, it is assumed that the shareholder was in the highest individual federal marginal income tax bracket at the time of each distribution of income or capital gains or upon redemption. State and local income taxes are not reflected in the calculations. Please note that after-tax returns are shown only for the Institutional Shares and may differ for each share class. After-tax returns are not relevant for a shareholder who holds fund shares in a tax-deferred account, such as an individual retirement account or a 401(k) plan. Also, figures captioned Return After Taxes on Distributions and Sale of Fund Shares may be higher than other figures for the same period if a capital loss occurs upon redemption and results in an assumed tax deduction for the shareholder.

Risk/Return Bar Chart and Table.

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If the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart.

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Risk/Return Bar Chart and Table.

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The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

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Risk/Return Summary Fee Table Includes the following information, in plain English under rule 421(d) under the Securities Act, after Item 2 Fees and expenses of the Fund This table describes the fees and expenses that you may pay if you buy and hold shared of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $[_____] in [name of fund family] funds. Shareholder Fees (fees paid directly from your investment) Example This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then you redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return per year and that the Fund's operating expenses remained the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be You would pay the following expenses if you did not redeem your shares The Example does not reflect sales charges (loads) on reinvested dividends [and other distributions]. If these sales charges (loads) were included, your costs would be higher. Portfolio Turnover The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was __% of the average value of its whole portfolio. Instructions. A.3.instructions.6 New Funds. For purposes of this Item, a "New Fund" is a Fund that does not include in Form N-1A financial statements reporting operating results or that includes financial statements for the Fund's initial fiscal year reporting operating results for a period of 6 months or less. The following Instructions apply to New Funds.

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This table describes the fees and expenses that you may pay if you buy and hold shared of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $[_____] in [name of fund family] funds. Include the narrative explanations in the order indicated. A Fund may modify the narrative explanations if the explanation contains comparable information to that shown. The narrative explanation regarding sales charge discounts is only required by a Fund that offers such discounts and should specify the minimum level of investment required to qualify for a discount. Modify the narrative explanation to state that Fund shares are sold on a national securities exchange at the end of the time periods indicated, and that brokerage commissions for buying and selling Fund shares through a broker are not reflected.

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Investment Objectives/Goals. Disclose the Fund's investment objectives or goals. A Fund also may identify its type or category (e.g., that it is a Money Market Fund or a balanced fund).

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Investment Objectives/Goals. Disclose the Fund's investment objectives or goals. A Fund also may identify its type or category (e.g., that it is a Money Market Fund or a balanced fund).

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Annual Fund Operating Expenses (ongoing expenses that you pay each year as a percentage of the value of your investment)

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Risk/Return Bar Chart and Table.

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If the Fund has annual returns for at least one calendar year, provide a table showing the Fund's (A) average annual total return; (B) average annual total return (after taxes on distributions); and (C) average annual total return (after taxes on distributions and redemption). A Money Market Fund should show only the returns described in clause (A) of the preceding sentence. All returns should be shown for 1-, 5-, and 10- calendar year periods ending on the date of the most recently completed calendar year (or for the life of the Fund, if shorter), but only for periods subsequent to the effective date of the Fund's registration statement. The table also should show the returns of an appropriate broad-based securities market index as defined in Instruction 5 to Item 22(b)(7) for the same periods. A Fund that has been in existence for more than 10 years also may include returns for the life of the Fund. A Money Market Fund may provide the Fund's 7-day yield ending on the date of the most recent calendar year or disclose a toll-free (or collect) telephone number that investors can use to obtain the Fund's current 7-day yield. For a Fund (other than a Money Market Fund or a Fund described in General Instruction C.3.(d)(iii)), provide the information in the following table with the specified captions AVERAGE ANNUAL TOTAL RETURNS (For the periods ended December 31, _____)

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This item represents Average Annual Total Returns. If a Multiple Class Fund offers a Class in the prospectus that converts into another Class after a stated period, compute average annual total returns in the table by using the returns of the other Class for the period after conversion.

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Disclose the portfolio turnover rate provided in response to Item 14(a) for the most recent fiscal year (or for such shorter period as the Fund has been in operation). Disclose the period for which the information is provided if less than a full fiscal year. A Fund that is a Money Market Fund may omit the portfolio turnover information required by this Item.

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Narrative Risk Disclosure.

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Narrative Risk Disclosure. A Fund may, in responding to this Item, describe the types of investors for whom the Fund is intended or the types of investment goals that may be consistent with an investment in the Fund.

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Risk/Return Summary Investment Objectives/Goals Include the following information, in plain English under rule 421(d) under the Securities Act, in the order and subject matter indicated

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Shareholder Fees (fees paid directly from your investment).

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Principal investment strategies of the Fund. Summarize how the Fund intends to achieve its investment objectives by identifying the Fund's principal investment strategies (including the type or types of securities in which the Fund invests or will invest principally) and any policy to concentrate in securities of issuers in a particular industry or group of industries.

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