MBB vs VMBS: Holdings Overlap
iShares · 11144 holdings · $39.1B · as of 2026-05-31
VMBSVanguard Mortgage-backed Securities Index Fund
Vanguard · 5112 holdings · $15.6B · as of 2026-05-31
How similar are MBB and VMBS?
iShares MBS ETF (MBB, by iShares) holds 11144 positions; Vanguard Mortgage-backed Securities Index Fund (VMBS, by Vanguard) holds 5112. They have 1212 holdings in common, and by portfolio weight the two funds are 17.2% identical. In practical terms the pair is lightly overlapping, with most of each portfolio distinct.
- Overlap by Weight
- 17.2%Sum of the smaller weight of each shared holding
- Shared Holdings
- 1212MBB holds 11144 · VMBS holds 5112
- Weight in Shared Holdings
- MBB 32%·VMBS 34%Share of each fund's weight in stocks both funds own
Based on each fund's latest official holdings. How is this calculated?
What makes each fund different
Only in MBB
9932 of 11144 positions (66.2% of the fund) are not held by VMBS. Showing the top 30 by weight.
- Ginnie Mae II Pool0.53%
- Fannie Mae Pool0.52%
- Ginnie Mae0.46%
- Fannie Mae Pool0.44%
- Fannie Mae Pool0.44%
- Fannie Mae Pool0.33%
Only in VMBS
3900 of 5112 positions (65.8% of the fund) are not held by MBB. Showing the top 30 by weight.
- G2SF 5.5 7/260.36%
- FN CC27620.29%
- FR SD41550.27%
- FR RQ01180.27%
- Uniform Mortgage-Backed Security, TBA0.25%
- FR RQ00940.24%
Performance
| Fund | 1M | YTD | 1Y | 3Y (ann.) | 5Y (ann.) | 10Y (ann.) | Yield |
|---|---|---|---|---|---|---|---|
| MBB | -0.2% | +0.4% | +3.9% | +4.7% | +0.3% | +1.2% | 4.33% |
| VMBS | -0.1% | +0.6% | +4.1% | +4.9% | +0.4% | +1.3% | 4.23% |
Total returns including dividends, from adjusted daily closes as of 2026-08-07. 3Y/5Y/10Y are annualized. Yield is trailing-12-month distributions over the last close. Past performance does not predict future results.
Project the growth of $10,000 in MBB vs VMBS →
Shared Holdings(1212)
The top 10 shared positions account for 12% of the overlap, led by Government National Mortgage Association, Ginnie Mae and Uniform Mortgage-Backed Securities.
| Government National Mortgage Association | 0.55% | 0.32% | 0.32% |
|---|---|---|---|
| Ginnie Mae | 0.95% | 0.29% | 0.29% |
| Uniform Mortgage-Backed Securities | 1.05% | 0.26% | 0.26% |
| Uniform Mortgage-Backed Security, TBA | 0.34% | 0.20% | 0.20% |
| Freddie Mac Pool | 0.22% | 0.20% | 0.20% |
| Government National Mortgage Association | 0.31% | 0.20% | 0.20% |
| Uniform Mortgage-Backed Securities | 0.30% | 0.18% | 0.18% |
| Uniform Mortgage-Backed Securities | 0.24% | 0.16% | 0.16% |
| Government National Mortgage Association | 0.20% | 0.16% | 0.16% |
| Ginnie Mae | 0.67% | 0.15% | 0.15% |
| Uniform Mortgage-Backed Security, TBA | 0.83% | 0.15% | 0.15% |
| Uniform Mortgage-Backed Securities | 0.15% | 0.18% | 0.15% |
| Uniform Mortgage-Backed Securities | 0.31% | 0.15% | 0.15% |
| Government National Mortgage Association | 0.15% | 0.28% | 0.15% |
| Government National Mortgage Association | 0.27% | 0.14% | 0.14% |
| Uniform Mortgage-Backed Security, TBA | 0.64% | 0.14% | 0.14% |
| Government National Mortgage Association | 0.22% | 0.14% | 0.14% |
| Government National Mortgage Association | 0.28% | 0.13% | 0.13% |
| Government National Mortgage Association | 0.13% | 0.14% | 0.13% |
| Uniform Mortgage-Backed Securities | 0.17% | 0.13% | 0.13% |
| Government National Mortgage Association | 0.30% | 0.12% | 0.12% |
| Ginnie Mae II Pool | 0.15% | 0.12% | 0.12% |
| Government National Mortgage Association | 0.45% | 0.12% | 0.12% |
| Uniform Mortgage-Backed Securities | 0.12% | 0.23% | 0.12% |
| Government National Mortgage Association | 0.41% | 0.12% | 0.12% |
Showing the top 250 of 1212 shared holdings by overlap weight.
Frequently Asked Questions
How much do MBB and VMBS overlap?
MBB and VMBS overlap by 17.2% of portfolio weight. They share 1212 holdings (MBB holds 11144 positions and VMBS holds 5112), based on each fund's latest SEC-reported holdings.
Is it redundant to own both MBB and VMBS?
The two portfolios are 17.2% identical by weight. Owning both is not redundant. Most of each portfolio is distinct, so the funds can serve different roles.
What are the biggest shared holdings of MBB and VMBS?
The largest positions held by both funds are Government National Mortgage Association, Ginnie Mae, Uniform Mortgage-Backed Securities, Uniform Mortgage-Backed Security, TBA and Freddie Mac Pool. Together the top 10 shared positions account for 12% of the total overlap.
What does MBB own that VMBS doesn't?
9932 positions (66.2% of MBB) are unique to MBB, led by Ginnie Mae II Pool, Fannie Mae Pool and Ginnie Mae. In the other direction, 3900 positions (65.8% of VMBS) are unique to VMBS.