How to Analyze Your Stock Portfolio: The 6 Checks Professionals Run
Returns tell you what happened. These six checks tell you why, and what could happen next: concentration, overlap, crash exposure, a fair benchmark, efficiency and dead weight.
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Is My Portfolio Diversified? How to Find Hidden Overlap
Owning many tickers is not the same as owning many bets. Here is how to find the overlap hiding in your ETFs and stocks, and how many independent positions you really have.
Key takeaways
- Diversification is about how your holdings move together, not how many you own.
- ETFs often overlap heavily: the largest US companies sit inside most broad and tech funds.
- A correlation matrix shows which holdings behave like one position.
- Count clusters, not tickers: that number is how many real bets you hold.
The ticker-count myth
“I own 15 stocks and four ETFs, so I am diversified.” It is one of the most common beliefs in self-directed investing, and one of the most expensive. Diversification only works when holdings respond differently to the same event. If a rate shock, a chip export ban or a recession hits all of them the same way, the number of tickers does not matter.
Step 1: Look inside your ETFs
Broad ETFs are weighted by market value, so the same handful of mega-cap companies sit at the top of most of them. If you hold an S&P 500 fund, a Nasdaq-100 fund and a technology fund, you likely own the largest tech names three times, plus again if you hold them directly.
How to check it:
- Download the full holdings list of each ETF from the issuer’s website.
- Multiply each underlying weight by how much of your portfolio sits in that ETF.
- Add your direct stock positions on top and sum by company.
The result is your look-through exposure: what you actually own, company by company.
| Look-through exposure | What it usually means |
|---|---|
| One company above 10% of the portfolio | A single-stock bet, whether you meant it or not |
| Top 5 companies above 35% | Your result depends on a few mega caps |
| One sector above 40% | One economic story drives your portfolio |
Step 2: Measure how your holdings move together
Overlap in names is the easy part. The harder part is different companies that trade as one. Two chip designers, a chip equipment maker and a cloud provider share almost nothing on paper, yet in a sell-off they often fall together.
Correlation measures this from −1 (always opposite) to +1 (always together). Calculate it from at least a year of weekly returns. As a working guide, pairs above roughly 0.7 should be treated as one risk, between 0.3 and 0.7 as partly related, and below 0.3 as genuinely different.
Correlations are not fixed. In crashes they tend to rise, so holdings that looked independent in calm markets can drop together exactly when you need them not to.
Step 3: Count your real bets
Group holdings that are highly correlated with each other into clusters. Each cluster is one bet. A portfolio of 18 positions can easily collapse into four or five clusters: US mega-cap tech, semiconductors, financials, energy and cash. That number, not 18, is your real diversification.
How to fix a portfolio that is less diversified than it looks
- Merge overlapping ETFs: keep the one that matches your goal and drop the duplicates.
- Size a cluster as one position: if five holdings act as one, cap their combined weight.
- Add exposures that behave differently: other regions, quality dividend payers, bonds or cash, depending on your goals.
- Re-check after each new purchase: overlap creeps back in one “great idea” at a time.
Frequently asked questions
Download each ETF’s holdings list, weight each company by how much of your portfolio is in that ETF, add your direct stock positions and sum by company. Any company that shows up large in several funds is overlap.
It holds about 500 companies, but it is weighted by market value, so a small group of the largest companies drives a large share of its moves. It is diversified across companies, less so across sectors and regions.
As a working rule, a correlation above about 0.7 means the two tend to move together, so treat them as one risk when sizing positions.
See your hidden overlap in about a minute.
Exent maps your correlation clusters and shows how many independent positions you really hold.
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Educational content, not investment advice. Examples are illustrative; past performance does not guarantee future results.