Trading term
What is Fund overlap?
Fund overlap is when two funds you own hold many of the same companies, so buying both concentrates your money instead of spreading it. It's the most common way a portfolio looks diversified and isn't.
Funds are sold by their label — global, large-company, technology, growth — and the labels sound like different things. Open the top-ten holdings of three of them and you'll often find the same handful of very large companies at the top of all three, because those companies are enormous and index funds weight by size.
So someone who buys a global fund for spread, a home-market fund for familiarity and a technology fund for growth may have bought the same dozen businesses three times, at three separate fees. The line count in the account went up. The number of distinct companies barely moved.
The check takes two minutes and works for any fund: open each one's factsheet, find the top-ten holdings, and see how many names repeat. If the same companies dominate all of them, the second and third fund are adding cost, not spread.
For example
You hold a global index fund, a large-company home-market fund and a technology fund. The three biggest holdings in all three are the same companies. You believed you owned three things; you own one bet in three wrappers.
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Explore Premium →Why it matters to you
Overlap quietly reverses the reason you diversified. You paid three fees, added three line items to track, and ended up more concentrated in a handful of very large companies than a single broad fund would have left you. When those companies have a bad year, all three of your funds have it at once.
⚠ More funds is not more diversification
The instinct is that a portfolio with six funds must be safer than one with two. It depends entirely on what's inside them. Six funds holding the same companies are one bet. Two genuinely different funds — say, global stocks and broad bonds — are two.