iShares U.S. Aggregate Bond Index Fund | WFBIX

Overview

About this Fund

High-Quality, Traditional Bonds
Replicates the Barclays US Aggregate Bond Index
Seeking Conservative Long-Term Total Returns

Investment Approach

Invests in a portfolio of assets whose performance seeks to match the performance of the Barclays U.S. Aggregate Bond Index.

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Performance

Returns

Average Annual
Cumulative
Calendar Year

	1y	3y	5y	10y	Incept. Performance data for certain classes of shares of certain funds are based on pre-class inception information dating back to an older class of fund shares. This information may be considered when assessing a fund's performance, but it does not represent actual performance of these classes of shares. The inception date noted under Key Fund Facts is the date the class of shares was incepted. See fund prospectus or fact sheet for details.
Total Return (%) Total return represents changes to the NAV and accounts for distributions from the fund.	4.42	1.91	2.63	3.56	4.96
Benchmark (%) Index: BBG Barc U.S. Aggregate Index.<br /><br /> Index returns are for illustrative purposes only. Index performance returns do not reflect any management fees, transaction costs or expenses. Indexes are unmanaged and one cannot invest directly in an index. Past performance does not guarantee future results.	4.48	2.03	2.74	3.77	5.16
Morningstar Category Avg. (%) Intermediate-Term Bond	3.98	2.37	2.51	4.56	-
Morningstar Ranking Rankings are based on total return excluding sales charges, independently calculated and not combined to create an overall ranking.	251/1024	637/901	328/769	459/564	-
Morningstar Quartile Rankings based on total return excluding sales charges, independently calculated and not combined to create an overall ranking.	2	3	2	4	-
Lipper Category Avg. (%) Core Bond Funds	3.96	2.18	2.43	4.45	-
Lipper Ranking Rankings are based on total return excluding sales charges.	121/509	299/447	149/380	241/293	-
Lipper Quartile Rankings are based on total return excluding sales charges.	1	3	2	4	-

Missing average annual returns data

	YTD	1m	3m	1y	3y	5y	10y	Incept. Performance data for certain classes of shares of certain funds are based on pre-class inception information dating back to an older class of fund shares. This information may be considered when assessing a fund's performance, but it does not represent actual performance of these classes of shares. The inception date noted under Key Fund Facts is the date the class of shares was incepted. See fund prospectus or fact sheet for details.
Total Return (%) Total return represents changes to the NAV and accounts for distributions from the fund.	2.97	1.94	2.97	4.42	5.83	13.88	41.93	248.09
Benchmark (%) Index: BBG Barc U.S. Aggregate Index.<br /><br /> Index returns are for illustrative purposes only. Index performance returns do not reflect any management fees, transaction costs or expenses. Indexes are unmanaged and one cannot invest directly in an index. Past performance does not guarantee future results.	2.94	1.92	2.94	4.48	6.20	14.48	44.72	263.38
Morningstar Category Avg. (%) Intermediate-Term Bond	3.13	1.70	3.13	3.98	7.28	13.18	56.22	-
Lipper Category Avg. (%) Core Bond Funds	3.20	1.81	3.20	3.96	6.70	12.81	55.21	-

Missing cumulative returns data

	2014	2015	2016	2017	2018
Total Return (%) Total return represents changes to the NAV and accounts for distributions from the fund.	5.94	0.38	2.53	3.39	-0.08
Benchmark (%) Index: BBG Barc U.S. Aggregate Index<br /><br /> Index returns are for illustrative purposes only. Index performance returns do not reflect any management fees, transaction costs or expenses. Indexes are unmanaged and one cannot invest directly in an index. Past performance does not guarantee future results.	5.97	0.55	2.65	3.54	0.01
Morningstar Category Avg. (%) Intermediate-Term Bond	5.18	-0.26	3.23	3.71	-0.50

Missing calendar year returns data

The performance quoted represents past performance and does not guarantee future results. Investment return and principal value of an investment will fluctuate so that an investor's shares, when sold or redeemed, may be worth more or less than the original cost. Current performance may be lower or higher than the performance quoted.

Growth of Hypothetical $10,000 The growth of hypothetical $10,000 chart reflects a hypothetical $10,000 investment and assumes reinvestment of dividends and capital gains. Fund expenses, including management fees and other expenses were deducted.

Performance chart data not available for display.

Growth of Hypothetical $10,000
Historical NAVs

iShares U.S. Aggregate Bond Index Fund ($)

Cum. Fund Perf. Since Inception: 248.09

Source: Lipper. Data reflects different methodology from the BlackRock calculated returns in the Returns tab. The $10,000 Hypothetical Over Time chart reflects a hypothetical $10,000 investment in the investor class of shares noted and does not assume the max sales charge. Had sales charge been included, returns would have been lower. The chart uses total return NAV performance and assumes reinvestment of dividends and capital gains. Fund expenses, including 12b-1 fees, management fees and other expenses were deducted. Performance for other share classes will vary.

Historical NAVs

Distributions

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Recent
Calendar Year

Chart
Table

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Ex-Date	Payable Date	Record Date	Total Distribution Current year distributions are not classified as “Income,” “Short-Term Capital Gains,” “Long-Term Capital Gains,” or “Return of Capital” until approximately 60 days following calendar year-end.	Income	ST Cap Gains	LT Cap Gains	Return of Capital

Chart
Table

Interactive chart displaying fund performance. Javascript is required.

Year	Total Distribution Current year distributions are not classified as “Income,” “Short-Term Capital Gains,” “Long-Term Capital Gains,” or “Return of Capital” until calendar year-end.	Income	ST Cap Gains	LT Cap Gains

Past distributions are not indicative of future distributions.
Click here, for the most recent distributions.

Key Facts

Size of Class (Millions) as of Apr 22, 2019 $1,216.1 M

Size of Fund (Millions) as of Apr 22, 2019 $1,491.2 M

Share Class launch date Feb 02, 2010

Asset Class Fixed Income

Morningstar Category Intermediate-Term Bond

Lipper Classification Core Bond Funds

Benchmark Index BBG Barc U.S. Aggregate Index

CUSIP 066922105

Distribution Frequency How often a distribution is paid by the fund. The most common distribution frequencies are annually, biannually and quarterly. Monthly

Number of Holdings as of Mar 29, 2019 3,797

Max Offer Price as of Apr 22, 2019 $10.02

Open to New Investors Yes

Turnover Percent as of Mar 31, 2019 274%

Portfolio Characteristics

Alpha (3y) Compared to BBG Barc U.S. Aggregate Index. Alpha is calculated at the portfolio level. A measure of performance on a risk-adjusted basis. Alpha takes the volatility (price risk) of a mutual fund and compares its risk-adjusted performance to a benchmark index. The excess return of the fund relative to the return of the benchmark index is a fund's alpha. as of Mar 31, 2019 -0.01

R-Squared (3y) as of Mar 31, 2019 99.80

Beta (3y) as of Mar 31, 2019 1.00

30 Day SEC Yield A standard calculation of yield introduced by the SEC in order to provide fairer comparison among funds. This yield reflects the interest earned after deducting the fund's expenses during the most recent 30-day period by the average investor in the fund. Negative 30-Day SEC Yield results when accrued expenses of the past 30 days exceed the income collected during the past 30 days. as of Mar 31, 2019 2.83%

Unsubsidized 30-Day SEC Yield Represents what a fund's 30-Day SEC Yield would have been had no fee waiver or expense reimbursement been in place over the period. as of Mar 31, 2019 2.83%

Yield to Maturity Yield to Maturity (YTM) is the discount rate that equates the present value of a bond's cash flows with its market price (including accrued interest). The Fund Average YTM is the weighted average of the fund's individual bond holding YTMs based upon Net Asset Value ('NAV'). The measure does not include fees and expenses. For callable bonds, YTM is the yield-to-worst. as of Mar 29, 2019 2.93%

Yield to Worst The average rate of return of the portfolio at current market prices, adjusting for optionality. as of Mar 29, 2019 2.93%

Average Coupon as of Mar 29, 2019 3.20%

Effective Duration Effective Duration measures the sensitivity of the price of a bond with or without embedded options to changes in interest rates, taking into account the likelihood of the bond being called, put and/or sunk prior to its final maturity date while incorporating after-tax impacts on the bond. The options-based duration model used by BlackRock employs certain assumptions and may differ from other fund complexes. Effective Duration is measured at the individual bond level, aggregated to the portfolio level, and adjusted for leverage, hedging transactions and non-bond holdings, including derivatives. as of Mar 29, 2019 5.49 yrs

Weighted Average Life Nominal Weighted Average Life is shown. Weighted Average Life is the average number of years for which each dollar of unpaid principal on a loan or mortgage remains outstanding. as of Mar 29, 2019 7.94 yrs

Best 3-Month Return Over the Last 3 Years 3 months ending Jan 31, 2019 3.47%

Worst 3-Month Return Over the Last 3 Years 3 months ending Nov 30, 2016 -3.24%

This information must be preceded or accompanied by a current prospectus. For standardized performance, please see the Performance section above.

Fees

as of current prospectus

Gross Expense Ratio	0.06%
Net Expense Ratio The difference between gross and net expense ratios are due to contractual and/or voluntary waivers, if applicable. Any applicable contractual waiver will be terminable upon 90 days’ notice. BlackRock may agree to voluntarily waive certain fees and expenses, which the adviser may discontinue at any time without notice. For this share class, the contractual waiver end date is Apr 30, 2019.	0.05%

Net Expense Ratio excluding Investment Related Expenses is 0.04%

Ratings

Lipper Leader

Lipper Leader Ratings

Expense iShares U.S. Aggregate Bond Index Fund received the following Expense ratings for the 3-, 5-, and 10-year periods, respectively: 5 (259 funds), 5 (208 funds), and 5 (148 funds). Lipper ratings for Expense reflect funds' expense minimization relative to peers with similar load structures.

Tax Efficiency iShares U.S. Aggregate Bond Index Fund received the following Tax Efficiency ratings for the 3-, 5-, and 10-year periods, respectively: 4 (447 funds), 4 (380 funds), and 3 (293 funds). Lipper ratings for Tax Efficiency (US) reflect funds' historical success in postponing taxable distributions relative to peers. Tax Efficiency (US) offers no benefit to investors in tax-sheltered accounts such as retirement plans.

Overall Lipper Leaders ratings based on an equal-weighted average of percentile ranks for each measure over 3-, 5-, and 10-year periods (if applicable) and do not take into account the effects of sales charges for these categories (Consistent Return, Preservation, Total Return, Expense, and Tax Efficiency) as of Mar 31, 2019 out of 442, 5,794, 447, 259 and 447 Funds, respectively in Lipper's Core Bond Funds classification.

Holdings

as of Mar 29, 2019

Name	Weight (%)
UNITED STATES TREASURY	38.89
FEDERAL NATIONAL MORTGAGE ASSOCIATION	12.87
GOVERNMENT NATIONAL MORTGAGE ASSOCIATION II	7.69
FEDERAL HOME LOAN MORTGAGE CORPORATION -GOLD	5.14
FEDERAL HOME LOAN MORTGAGE CORPORATION	2.55

Name	Weight (%)
BANK OF AMERICA CORP	0.56
JPMORGAN CHASE & CO	0.51
EUROPEAN INVESTMENT BANK	0.46
KFW	0.44
AT&T INC	0.42

as of Mar 29, 2019

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Allocations subject to change.

as of Mar 29, 2019

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The fund itself has not been rated by an independent rating agency. Credit quality ratings on underlying securities of the fund are received from S&P, Moody’s and Fitch and converted to the equivalent S&P major rating category. This breakdown is provided by BlackRock and takes the median rating of the three agencies when all three agencies rate a security the lower of the two ratings if only two agencies rate a security and one rating if that is all that is provided. Unrated securities do not necessarily indicate low quality. Below investment-grade is represented by a rating of BB and below. Ratings and portfolio credit quality may change over time.

Negative weightings may result from specific circumstances (including timing differences between trade and settle dates of securities purchased by the funds) and/or the use of certain financial instruments, including derivatives, which may be used to gain or reduce market exposure and/or risk management. Certain transactions the funds may utilize may give rise to a form of leverage through either (a) additional market exposure or (b) borrowing capital in an attempt to increase investment return. The use of such transactions includes certain leverage-related risks, including potential for higher volatility, greater decline of the fund’s net asset value and fluctuations of dividends and distributions paid by the fund.

Allocations are subject to change.

Portfolio Managers

James Mauro

Scott Radell

Portfolio Manager

Literature

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Important Information

Carefully consider the Funds' investment objectives, risk factors, and charges and expenses before investing. This and other information can be found in the Funds' prospectuses or, if available, the summary prospectuses which may be obtained by visiting the iShares Fund and BlackRock Fund prospectus pages. Read the prospectus carefully before investing.

The portfolio holdings information shown for iShares U.S. Aggregate Bond Index Fund (the “Fund”) on this site are the portfolio holdings of U.S. Total Bond Index Master Portfolio (the “Master Portfolio”). The Fund is a “feeder” fund that invests all of its assets in the Master Portfolio, a mutual fund that has the same investment objectives and strategies as the Fund. All investments are made at the level of the Master Portfolio. The Fund’s investment results will correspond directly to the investment results of the Master Portfolio. Because the Master Portfolio may have other investors, the percentage of the Master Portfolio held by the Fund may change from time to time. As of November 30, 2018, the Fund held 16.07% of the Master Portfolio.

Bond values fluctuate in price so the value of your investment can go down depending on market conditions.

Fixed income risks include interest-rate and credit risk. Typically, when interest rates rise, there is a corresponding decline in bond values. Credit risk refers to the possibility that the bond issuer will not be able to make principal and interest payments.

Obligations of US govt. agencies are supported by varying degrees of credit but generally are not backed by the full faith and credit of the US govt.

The fund may use derivatives to hedge its investments or to seek to enhance returns. Derivatives entail risks relating to liquidity, leverage and credit that may reduce returns and increase volatility.

An index fund has operating and other expenses while an index does not. As a result, while an Index fund will attempt to track the applicable index as closely as possible, it will tend to underperform the index to some degree over time.

Performance results reflect past performance and are no guarantee of future results. Investment return and principal value of shares will fluctuate so that shares, when redeemed, may be worth more or less than their original cost. All returns assume reinvestment of all dividends. Performance information shown without sales charge would have been lower if the applicable sales charge had been included. Performance during periods of exceptional market conditions should not be expected to be repeated in a normal market environment. Current performance may be lower or higher than the performance data quoted.

Investing involves risk, including possible loss of principal.

Fund details, holdings and characteristics are as of the date noted and subject to change.

Yields are based on income earned for the period cited and on the Fund's NAV at the end of the period.

Some BlackRock funds make distributions of ordinary income and capital gains at calendar year end. Those distributions temporarily cause extraordinarily high yields. There is no assurance that a fund will repeat that yield in the future. Subsequent monthly distributions that do not include ordinary income or capital gains in the form of dividends will likely be lower.

The Funds are distributed by BlackRock Investments, LLC (together with its affiliates, “BlackRock”).

© 2019 BlackRock, Inc. All rights reserved. BLACKROCK, BLACKROCK SOLUTIONS, BUILD ON BLACKROCK, ALADDIN, iSHARES, iBONDS, iSHARES CONNECT, FUND FRENZY, LIFEPATH, SO WHAT DO I DO WITH MY MONEY, INVESTING FOR A NEW WORLD, BUILT FOR THESE TIMES, the iShares Core Graphic, CoRI and the CoRI logo are registered and unregistered trademarks of BlackRock, Inc., or its subsidiaries in the United States and elsewhere. All other marks are the property of their respective owners.

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