IWM vs VO: how much do they really overlap?
IWM (iShares Russell 2000 ETF, tracking the Russell 2000) and VO (Vanguard Mid-Cap ETF, tracking the CRSP US Mid Cap) overlap by roughly 0% by weight. 0 of IWM's top 10 holdings also appear in VO. A 50/50 blend of the two behaves like about 1373 equally-weighted bets (diversification grade A). In short, the two funds hold almost none of the same securities — they are complementary, not redundant.
The same companies, in both funds
These 0 holdings appear in both IWM and VO. The weight columns show how much of each fund each name represents.
| Holding | in IWM | in VO |
|---|
Only in IWM
iShares Russell 2000 ETF — US small-cap. Its biggest holdings that VO doesn’t have:
| XTSLA BLK CSH FND TREASURY SL AGENCY | 0.46% |
| MOGA MOOG INC CLASS A | 0.39% |
| BTSG BRIGHTSPRING HEALTH SERVICES INC | 0.38% |
| HUT HUT CORP | 0.36% |
| UMBF UMB FINANCIAL CORP | 0.35% |
| CYTK CYTOKINETICS INC | 0.34% |
| VSAT VIASAT INC | 0.32% |
| GKOS GLAUKOS CORP | 0.31% |
Only in VO
Vanguard Mid-Cap ETF — US mid-cap. Its biggest holdings that IWM doesn’t have:
| VRT Vertiv Holdings Co. Class A | 1.22% |
| WDC Western Digital Corp. | 1.06% |
| STX Seagate Technology Holdings plc | 1.04% |
| PWR Quanta Services Inc. | 1.04% |
| HWM Howmet Aerospace Inc. | 1.04% |
| CMI Cummins Inc. | 0.95% |
| DDOG Datadog Inc. Class A | 0.83% |
| BE Bloom Energy Corp. Class A | 0.79% |
So — essentially different. Should you hold both?
IWM and VO hold almost none of the same securities — they are complementary, not redundant. Held together they genuinely broaden your exposure — a 50/50 blend reaches ~1373 effective positions (grade A), because they hold largely different securities.
Holdings as of — IWM: Jul 30, 2026 (iShares (BlackRock)); VO: Jun 30, 2026 (Vanguard). Refreshed monthly. Overlap is measured across each fund’s largest holdings (top 50); the diffuse long tail barely moves the math.
See this for YOUR whole portfolio, free →IWM vs VO — FAQ
- How much do IWM and VO overlap?
- IWM and VO overlap by approximately 0% measured by portfolio weight — that is the share of the smaller fund's holdings (by weight) that also sit inside the other. 0 of IWM's 10 largest holdings are also held by VO. They share 0 of their listed top holdings in total.
- Is it redundant to hold both IWM and VO?
- Because they hold almost none of the same securities — they are complementary, not redundant, holding both is not redundant — each fund covers largely different holdings, so together they broaden your exposure. A 50/50 blend has an effective 1373 positions and a A diversification grade.
- What does VO hold that IWM doesn't?
- VO's largest holdings that IWM doesn't hold include VRT, WDC, STX, PWR, HWM. Its category is US mid-cap, versus IWM's US small-cap.
- Which is more concentrated, IWM or VO?
- IWM's top 10 holdings are 26% of its listed weight; VO's are 27%. The more concentrated fund leans harder on its largest names.