Data as of Oct 28, 2026.
IWO vs MBB: Differences, Returns & Fees
Over the year to Oct 28, 2026, IWO returned +7.9% to MBB's −0.8%; 0% of their weight is in the same names.
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Net assets: $14.0bn on Oct 27, 2026 for iShares Russell 2000 Growth ETF, and $35.5bn on Oct 28, 2026 for iShares MBS ETF.
Pair scorecard
MBB costs 0.20 points a year less; their one-year returns differ by 8.7 points; MBB is 2.6 times larger.
| Measure | IWO | MBB |
|---|---|---|
| Return | ||
| Total return, 1 year | +7.9% | −0.8% |
| Drawdown | ||
| Below its high | 9.9%, high on Aug 14, 2026 | |
| Benchmark | ||
| What it tracks | Russell 2000 Growth Index | Bloomberg U.S. MBS Index |
| Cost and size | ||
| Expense ratio | 0.24% | 0.04% |
| Net assets, as of Oct 26, 2026 | $13.7bn | $35.6bn |
| Holdings | ||
| Holdings in common | 0% | |
| In the S&P 500, by weight | 0% | |
| Top ten holdings, share of the fund | 6.4% | |
Holdings in common uses holdings dated Oct 27, 2026. Method
Risk and return
Mar 23, 2007 to Oct 23, 2026 · 1,022 weekly returnsEach against its own benchmark: IWO against VTWG, Oct 1, 2010 to Oct 23, 2026; MBB against SPMB, Feb 6, 2009 to Oct 23, 2026.
IWO returned more: +391.6% to +63.4%. MBB swung less: 4.2% to 24.0%. MBB fell less at its worst: −17.4% to −56.5%.
Full scorecard
19 measures, with how each is measured Open ↓
| Measure | IWO | MBB | Edge | How it is measured |
|---|---|---|---|---|
| Return | ||||
| Total return | +391.6% | +63.4% | IWO | Price change plus distributions, reinvested. |
| Annualized | +8.4% | +2.5% | IWO | Total return as a yearly rate. |
| Price return | +324.5% | −9.6% | IWO | Price change alone, distributions left out. |
| Risk | ||||
| Volatility | 24.0% | 4.2% | MBB | Spread of weekly returns, annualized. Lower is steadier. |
| Downside deviation | 16.8% | 2.9% | MBB | Like volatility, counting only weeks below the Treasury bill rate. |
| Max drawdown | −56.5% | −17.4% | MBB | Deepest fall from a high to the low after it. |
| Upside capture | 100.2% | 77.8% | Share of its benchmark's rise caught in the weeks it rose. | |
| Downside capture | 100.1% | 78.4% | Share of its benchmark's fall taken in the weeks it fell. Lower is better. | |
| Beta | 1.00 | 0.76 | Not an edge | How far it moves for each 1% its benchmark moves. |
| R squared | 1.00 | 0.76 | Not an edge | Share of its weekly moves its benchmark explains. |
| Risk-adjusted | ||||
| Sharpe | 0.39 | 0.24 | IWO | Return above Treasury bills per unit of volatility. |
| Sortino | 0.56 | 0.35 | IWO | Return above Treasury bills per unit of downside deviation. |
| Treynor | 0.111 | 0.009 | Return above Treasury bills per unit of beta. | |
| Calmar | 0.15 | 0.15 | IWO (slight) | Annualized return divided by the max drawdown. |
| Against the benchmark | ||||
| Benchmark | VTWG | SPMB | The ETF each fund is measured against. | |
| Alpha | 0.0% a year | +0.1% a year | Not significant | Yearly return beyond what its beta to the benchmark predicts. |
| Alpha t-stat | 0.06 | 0.26 | Not an edge | How sure the alpha is. Below 2, it could be chance. |
| Alpha range | −0.7% to +0.7% | −0.8% to +1.1% | Includes zero | The 95% range for the yearly alpha. |
| Information ratio | 0.01 | −0.03 | Return against its benchmark per unit of tracking error. | |
| Tracking error | 1.5% | 2.3% | Not an edge | How far weekly returns stray from the benchmark, annualized. |
Computed by ETFIQ from Tiingo daily prices and ETFIQ's distribution records, 1,022 weekly returns. Cash rate: the 13-week Treasury bill.
What they share
By the books each fund has filed, IWO and MBB hold 0% of their money in the same securities at the same weight. Holdings dated Oct 27, 2026.
half
0% in common
Only in one fund ↓
Side by side
IWO and MBB on the fields both publish, as of Oct 28, 2026. Source: ETFIQ.
IWO and MBB do different jobs. What does each one do in a portfolio?
- What each follows. IWO follows Russell 2000 Growth Index and MBB follows Bloomberg U.S. MBS Index.
- Holdings in common. 0% of the weight is in the same securities (holdings dated Oct 27, 2026).
- One-year total return. Over 1 year to Oct 28, 2026 IWO returned +7.9% and MBB −0.8% with distributions reinvested, a gap of 8.7 points.
Data as of Oct 28, 2026.
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IWO
IWO tracks the Russell 2000 Growth. Over the year to Oct 28, 2026 it returned +7.9% with distributions reinvested, against +8.0% for its benchmark, the Russell 2000 Growth Index. The prospectus expense ratio is 0.24% a year. By its holdings published by its issuer for Oct 27, 2026, 0% of the fund by weight is stocks the S&P 500 also holds, across 1,122 positions, with the top ten at 6.4%. It sat 9.9% below its high of Aug 14, 2026 on Oct 28, 2026.
MBB
MBB tracks an index of mortgage-backed securities. Over the year to Oct 28, 2026 it returned −0.8% with distributions reinvested, against −1.1% for its benchmark, the Bloomberg U.S. MBS Index. The prospectus expense ratio is 0.04% a year.
Questions people ask
- Which returned more over the last year, IWO or MBB?
- In the year to Oct 28, 2026, with distributions reinvested, IWO returned +7.9% and MBB −0.8%.
- Which is cheaper, IWO or MBB?
- MBB is cheaper, by 0.20 percentage points a year. That is about $20 on $10,000 held for a year. Fees come from each fund's prospectus.
Links are sources, not endorsements. A comparison is not a recommendation.
How this is computed
Overlap adds up the smaller of the two weights for each security both funds hold.
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ETFIQ, IWO against MBB, data as of Oct 28, 2026. https://etfiq.com/compare/any/iwo-vs-mbb
ETFIQ. (Oct 28, 2026). IWO against MBB. Retrieved from https://etfiq.com/compare/any/iwo-vs-mbb
[IWO against MBB (ETFIQ, Oct 28, 2026)](https://etfiq.com/compare/any/iwo-vs-mbb)
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