The world of exchange-traded funds (ETFs) has grown quickly in recent years, with hundreds of new thematic, active, leveraged and niche funds. This makes it harder than ever for investors to pick the right ones.
One of the most misunderstood concepts we’ve seen investors face when it comes to ETFs is the idea of “true diversification.”
You may assume that owning multiple ETFs automatically provides diversification. But in reality, they often hold the same risks packaged in different wrappers.
For example, an investor might hold an S&P 500 index ETF, a total U.S. market ETF, and a large-cap growth or technology ETF.
At first glance, these look like three different investments. But in reality, the same handful of mega-cap technology stocks [like Apple Inc. 
(AAPL), Microsoft Corp. (MSFT), Nvidia Corp. (NVDA), Amazon.com Inc. (AMZN) and Alphabet Inc. (GOOGL)] often dominate all three. When those stocks drop, the whole portfolio falls together, even though it appears diversified.
Common pitfalls include:
- Overlap between ETF holdings leading to unintentional concentration,
- Misunderstanding what an ETF actually invests in or how it behaves, and
- Confusing marketing labels with genuine diversification.
The solution is to look beyond ETF names and analyze how your holdings behave. Here are a few things you should evaluate before investing in an ETF.
- Compare the largest holdings across ETFs to avoid unintentionally owning the same companies multiple times.
- Make sure ETFs capture different investment styles (growth, value, low volatility) and target different industries.
- Review how ETFs behaved in past market downturns to ensure they don’t all move in sync.
True diversification comes from combining ETFs that have different return drivers, not just stacking similar ones.
This month, I’m asking the AAII Community if anyone else has run into hidden ETF overlap.
When reviewing your ETF portfolio, how confident are you that each ETF adds a unique source of return rather than overlapping with what you already own?
Please visit the Mutual Funds & ETFs Community to join the discussion and connect with other individual investors.
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DAVE G from TX posted 5 months ago:
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