ETF comparison
MBB vs SPAB
Both US Aggregate Bond.
iShares MBS ETF · State Street SPDR Portfolio Aggregate Bond Index ETF
Holdings overlap
466 positions appear in both funds. Buying equal dollars of MBB and SPAB would leave roughly 5.8% of each dollar exposed to the same underlying securities.
Unmatched is the part of a fund's weight the other fund doesn't match: names only it holds, plus any extra weight it puts in names both funds hold.
Side by side
Sub-score comparison
Tracking quality isn't part of the composite — see what we don't score for why.
Cost difference
SPAB is 1 bps cheaper than MBB. On a $100,000 position that's about $10/yr more in fees for MBB.
Fee figure is the annual expense charged on $100,000. To see how the gap compounds over a multi-decade holding period, open the cost calculator pre-filled with MBB vs SPAB.
Top shared holdings
466 shared in total| # | Holding | In MBB | In SPAB | Overlap |
|---|---|---|---|---|
| 1 | Fannie Mae | 0.41% | 0.21% | 0.21% |
| 2 | Fannie Mae | 0.29% | 0.15% | 0.15% |
| 3 | Fannie Mae | 0.14% | 0.12% | 0.12% |
| 4 | Fannie Mae | 0.28% | 0.12% | 0.12% |
| 5 | Government National Mortgage Association | 0.15% | 0.11% | 0.11% |
| 6 | Freddie Mac | 0.23% | 0.11% | 0.11% |
| 7 | Fannie Mae | 0.16% | 0.11% | 0.11% |
| 8 | Government National Mortgage Association | 0.21% | 0.11% | 0.11% |
| 9 | Fannie Mae | 0.11% | 0.13% | 0.11% |
| 10 | Freddie Mac | 0.11% | 0.10% | 0.10% |
| 11 | Government National Mortgage Association | 0.10% | 0.10% | 0.10% |
| 12 | Fannie Mae | 0.10% | 0.11% | 0.10% |
Only in MBB
10,743 total- Government National Mortgage Association 1.05%
- Freddie Mac 0.98%
- UMBS, TBA 0.85%
- UMBS, TBA 0.70%
- Government National Mortgage Association 0.53%
- Government National Mortgage Association 0.51%
- Government National Mortgage Association 0.51%
- Government National Mortgage Association 0.49%
- Fannie Mae 0.49%
- Freddie Mac 0.47%
Only in SPAB
7,819 total- United States Treasury 0.79%
- United States Treasury 0.44%
- United States Treasury 0.43%
- United States Treasury 0.42%
- United States Treasury 0.40%
- United States Treasury 0.40%
- United States Treasury 0.39%
- United States Treasury 0.38%
- United States Treasury 0.37%
- United States Treasury 0.37%
Related comparisons
More comparisons with MBB
- MBB vs BND · Vanguard Total Bond Market Index Fund ETF Shares 5.4%
- MBB vs FBND · Fidelity Total Bond ETF 5.2%
- MBB vs VCRB · Vanguard Core Bond ETF 3.2%
- MBB vs JCPB · JPMorgan Core Plus Bond ETF 2.3%
- MBB vs AGGY · WisdomTree Yield Enhanced U.S. Aggregate Bond Fund 1.6%
- MBB vs BINC · iShares Flexible Income Active ETF 0.9%
More comparisons with SPAB
- SPAB vs TLT · iShares 20+ Year Treasury Bond ETF 4.9%
- SPAB vs BOND · PIMCO Active Bond Exchange-Traded Fund 3.2%
- SPAB vs NEAR · iShares Short Duration Bond Active ETF 3.0%
- SPAB vs PYLD · PIMCO ETF Trust - PIMCO Multisector Bond Active Exchange-Traded Fund 2.1%
- SPAB vs VUSB · Vanguard Ultra-Short Bond ETF 1.8%
- SPAB vs JPST · JPMorgan Ultra-Short Income ETF 1.3%
Percentages are holdings overlap with the named fund.
Open MBB or SPAB at a brokerage
Both funds trade commission-free at major US brokerages.
Affiliate links — opening an account through these earns PlainIndex a one-time referral. Scoring is computed before any affiliate consideration; see our methodology and funding disclosure.
Holdings overlap is the sum of min(weight_a, weight_b) over positions
matched on ISIN (CUSIP fallback). Methodology: see
/methodology/.
Comparing two funds doesn't endorse swapping one for the other. Tax-lot history, account type, and personal goals matter — PlainIndex publishes data and methodology, not investment advice.