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ETF comparison

MBB vs SPMB

Both US Aggregate Bond.

iShares MBS ETF · State Street SPDR Portfolio Mortgage Backed Bond ETF

Holdings overlap

Weighted by ISIN/CUSIP
15.0 %

826 positions appear in both funds. Buying equal dollars of MBB and SPMB would leave roughly 15.0% of each dollar exposed to the same underlying securities.

MBB only 89.3% Shared 15.0% SPMB only 83.2%
In MBB only
10,325 positions
Shared
826 positions
In SPMB only
1,827 positions

Side by side

MBB

iShares MBS ETF

iShares · US Aggregate Bond

88 composite / 100
Expense ratio
0.040%
Net assets
$39.63B
TTM yield
4.30%
Top-10 conc.
11.7%
SPMB

State Street SPDR Portfolio Mortgage Backed Bond ETF

State Street · US Aggregate Bond

86 composite / 100
Expense ratio
0.040%
Net assets
$7.07B
TTM yield
4.11%
Top-10 conc.
13.6%

Sub-score comparison

96
Cost
96
52
Tax efficiency
52
100
Liquidity
93
98
Concentration
95
—
Tracking quality
—
MBB sub-score SPMB

Tracking quality isn't part of the composite — see what we don't score for why.

Cost difference

Expense ratios are effectively identical (0.040% vs 0.040%).

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 SPMB.

Top shared holdings

826 shared in total
# Holding In MBB In SPMB Overlap
1 Fannie Mae 0.45% 0.50% 0.45%
2 Fannie Mae 0.32% 0.39% 0.32%
3 Freddie Mac 0.51% 0.32% 0.32%
4 Government National Mortgage Association 0.32% 0.32% 0.32%
5 Fannie Mae 0.30% 0.27% 0.27%
6 Government National Mortgage Association 0.31% 0.27% 0.27%
7 Government National Mortgage Association 0.29% 0.26% 0.26%
8 Government National Mortgage Association 0.36% 0.23% 0.23%
9 Fannie Mae 0.22% 0.47% 0.22%
10 Government National Mortgage Association 0.55% 0.22% 0.22%
11 Government National Mortgage Association 0.37% 0.19% 0.19%
12 Government National Mortgage Association 0.23% 0.19% 0.19%

Only in MBB

10,325 total
  • BLACKROCK CASH FUNDS 5.90%
  • Freddie Mac 1.07%
  • Government National Mortgage Association 1.00%
  • UMBS, TBA 0.57%
  • Government National Mortgage Association 0.56%
  • Fannie Mae 0.53%
  • Government National Mortgage Association 0.53%
  • UMBS, TBA 0.50%
  • Government National Mortgage Association 0.45%
  • Fannie Mae 0.45%

Only in SPMB

1,827 total
  • Freddie Mac 0.92%
  • Freddie Mac 0.89%
  • Freddie Mac 0.64%
  • Freddie Mac 0.60%
  • UMBS, TBA 0.60%
  • Fannie Mae 0.54%
  • Government National Mortgage Association 0.52%
  • Freddie Mac 0.48%
  • UMBS, TBA 0.48%
  • Government National Mortgage Association 0.45%

Open MBB or SPMB at a brokerage

Both funds trade commission-free at major US brokerages.

Open at Fidelity

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.