MBB
iShares MBS ETF
iShares MBS ETF is an exchange-traded fund incorporated in the USA. The ETF seeks to track the investment results of an index composed of investment-grade mortgage-backed pass-through securities issued and/or guaranteed by U.S. government agencies.
Mortgage
FIXED INCOME
Passive
MANAGEMENT STYLE
41.1 B
ASSETS UNDER MGMT
4 bp
EXPENSES
Fund Basics
| Fund sponsor | BlackRock Fund Advisors |
| Category | Mortgage |
| Asset class | Fixed Income |
| Website | link... |
| Inception date | Mar 13, 2007 |
| Assets (mns) | $41,077 |
| Expense ratio | 4 bp |
Constituent Breakdown
| No. of constituents | 1,032 |
| No. of distinct issuers | 393 |
| Coverage | 91% |
| Fixed/floating rate | 100% / 0% |
| Investment grade | 100% |
| Inflation protected | 0% |
| Non-standard maturity (callable, etc.) | 100% |
Fund Structure
| Regulation | Open-End Investment Company |
| Distributions | Monthly |
| Taxation | 1099 |
| Bond selection | |
| Weighting | Market Cap |
| Smart-beta | No |
| Derivatives-based | No |
| Options available | Yes |
| Currency hedged | No |
| Fund of funds | No |
Top 10 Holdings
| BLACKROCK CASH CL INST SL AGENCY | 3.5 % |
| FHLMC 30YR UMBS SUPER - 2.0 2051-05-01 | 0.9 % |
| GNMA2 30YR - 2.0 2051-10-20 | 0.6 % |
| GNMA2 30YR - 2.0 2051-12-20 | 0.6 % |
| FHLMC 30YR UMBS SUPER - 2.0 2051-04-01 | 0.6 % |
| GNMA2 30YR - 2.5 2051-07-20 | 0.5 % |
| FNMA 30YR UMBS - 2.0 2051-11-01 | 0.5 % |
| FNMA 30YR UMBS SUPER - 2.0 2051-07-01 | 0.5 % |
| GNMA2 30YR - 6.5 2054-07-20 | 0.4 % |
| GNMA2 30YR - 5.0 2054-11-20 | 0.4 % |
Issuer Type Breakdown
Top Issuers
| FANNIE MAE | 40.9 % |
| FREDDIE MAC | 26.5 % |
| GINNIE MAE | 23.6 % |
Historical Performance
Standardized Performance (as of 08/29/2025)
| YTD | 1 YR | 2 YR | 3 YR | 5 YR | 10 YR | 20 YR | Incep. | |
|---|---|---|---|---|---|---|---|---|
| Price Returns | 2.9% | -0.9% | 1.3% | -0.8% | -3.1% | -1.4% | -- | -0.4% |
| Dividend Yield | 1.5% | 2.4% | 3.2% | 3.1% | 2.4% | 2.5% | -- | 2.9% |
| Total Returns | 4.4% | 1.5% | 4.5% | 2.3% | -0.8% | 1.1% | -- | 2.5% | Ann. Volatility | 5.8% | 5.9% | 6.9% | 7.7% | 6.7% | 5.2% | -- | 4.6% |
Market Correlations
| versus... | Beta | R-squared |
| S&P 500 | 0.34 | 44% |
| MSCI EAFE | 0.36 | 55% |
| MSCI Emg Mkts | 0.34 | 53% |
Liquidity Measures
| Avg. volume (000) | 2,637 |
| ADV traded (mns) | $249 |
| Turnover | 0.6% |
| Avg. Bid/Ask (% of price) | 0.01% |
Technical Indicators
| Recent close | $94.43 |
| 30d moving avg. | $93.49 |
| Annualized volatility | 7.9% |
| Relative strength (RSI) | 61 |
| Short interest | 0.3% |
Distributions
Assets Under Management (mns)
Money Flows (mns)
Short Interest (as % of shares outstanding)
Long Money Flows (mns)
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Credit Quality
Duration
Macaulay Duration
Modified Duration
SHORT
MED.
LONG TERM
8.8 yrs
Modified Duration
◁ INSENSITIVE
EXTREMELY SENSITIVE ▷
8.8%
ⓘ Our analysis shows this fund is likely to be moderately sensitive to changes in interest rates
Interest Rate Sensitivity Analysis
| Change in YTM |
New YTM |
Est. Price Change |
New Price |
|---|---|---|---|
| +300 bp | --% | --% | $-- |
| +200 bp | --% | --% | $-- |
| +150 bp | --% | --% | $-- |
| +100 bp | --% | --% | $-- |
| +75 bp | --% | --% | $-- |
| +50 bp | --% | --% | $-- |
| +25 bp | --% | --% | $-- |
| 0 bp | --% | --% | $-- |
| -25 bp | --% | --% | $-- |
| -50 bp | --% | --% | $-- |
| -75 bp | --% | --% | $-- |
| -100 bp | --% | --% | $-- |
| -150 bp | --% | --% | $-- |
| -200 bp | --% | --% | $-- |
| - 300bp | --% | --% | $-- |
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Yields
Disposition of YTM
Distribution Yield (Trailing 12 Months)
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ETF Research Center Fund Rating
The ALTAR Score™ is our measure of an ETF's overall investment merit. For fixed income funds, the Score is an estimate of risk-adjusted yield to maturity (calculation shown below). In effecient markets, the plot of ALTAR Scores™ vs. Duration should resemble the familiar yield curve. Funds that sit above the curve may offer better risk-adjusted returns than those that sit below the curve.
ALTAR Score™
MBB
5.0%
Cat. Avg
4.7%
Fund Category: Mortgage
| Adj. Yield to Maturity | -- bp |
| Less: Annual "default factor" | -- bp |
| Less: Expenses | 4 bp |
| Equals: ALTAR Score™ | 5.0% |
ALTAR Score™ vs. Duration (Mortgage Bond ETFs)
Expense Analysis
| Peer Group | Passive Mortgage Fixed Income ETFs |
| # of ETFs | 4 |
| Avg. Expense Ratio | 9.3 bp |
| Std. Deviation | 9.1 bp |
| MBB (4 bp) Percentile rank | 28 |
Peer Group Expense Ratio Distribution
Total Cost of Ownership (TCO) Comparison
| Expense (bp) (A) |
Avg. Bid/Ask (bp) (B) |
TCO (bp) (A)+(B) |
|
|---|---|---|---|
| MBB | 4.0 | 1.2 | 5.2 |
| Peer Avg. | 32.5 | 15.7 | 48.1 |
For a detailed cost analysis of this and any other ETF use the TCO Comparison Tool .