A common beginner portfolio: VOO, VTI and QQQ. Three funds sounds diversified. In practice, it's largely the same companies bought three times.
Two ideas: overlap and weight
- Overlap is how many of the same companies two funds hold.
- Weight is how much of each fund those companies make up.
Weight is what really matters. Two funds can share hundreds of tiny holdings and still behave differently. But if they share the same ten giants at large weights, they'll move almost in lockstep.
How the big three stack up
| Fund | What it holds | Relationship |
|---|---|---|
| VOO | The 500 largest U.S. companies | Every VOO stock is also in VTI |
| VTI | Nearly the entire U.S. market: large, mid and small companies | Its biggest holdings are the same as VOO's |
| QQQ | 100 of the largest non-financial Nasdaq companies | Its top holdings overlap heavily with VOO's top holdings |
Because all three are weighted by company size, the same mega-cap tech names sit at the top of each one. Adding VTI to VOO mostly adds a thin layer of mid and small companies. Adding QQQ mostly increases your bet on the largest tech stocks.
Is overlap bad?
Not necessarily. It's a problem only when you don't know about it. If you hold QQQ on purpose because you want more tech, that's a choice. If you hold VOO, VTI and QQQ thinking you're spread out, you're taking a much bigger tech bet than you realize.
How to check your own overlap
- Pull up the top 10 holdings and their weights for each fund. Free sites like stockanalysis.com list them.
- Add up how much of your total portfolio sits in each of the biggest names across all your funds.
- If a few companies make up far more than you intended, simplify. One broad fund often does the job of three.
This matters a lot for AI investors in particular: the biggest AI names are already the biggest holdings in every broad index fund. Before adding an AI ETF, check how much of it you already own.
Educational only, not investment advice.