Sector exposure: how much of your portfolio sits in one sector
Sector exposure is the share of your portfolio riding on one part of the economy. Value every position, group the values by sector, and divide: the largest of those percentages is the number. It matters because the names inside a sector move on the same news, so eight tickers in one sector are closer to one bet than to eight.
What sector exposure is
A sector is a group of companies that make money the same way and lose it the same way. When rates move, banks reprice together. When a fab slips a quarter, every semiconductor name gets the same headline. The businesses are genuinely different, and on the days that matter they behave like one.
That is why sector exposure is a risk measure rather than a taste. Owning five technology names instead of one does spread company risk: a single accounting scandal cannot take the whole book. It does nothing about the risk the five share. A repricing of the sector arrives at every position on the same morning, in the same direction, and the number of tickers on your screen does not soften it.
The measure has two halves and they answer different questions. Your largest-sector share says how much rides on your biggest bet. Your sector count says how many separate parts of the economy sit under the book. Most people have added up neither, and the guess is almost always lower than the arithmetic.
How to measure it
The measure
Six steps, all of them arithmetic you can do in a spreadsheet:
- Value each position: share count times current price, or the dollar amount if that is how you track it.
- Add the position values to get the book total.
- Tag every position with its sector.
- Sum the position values within each sector.
- Divide each sector sum by the book total. Those are your sector weights.
- The largest weight is your largest-sector share. The number of distinct sectors with a non-zero weight is your sector count.
Two rules decide what enters the arithmetic, and Clavix applies both. A broad fund is left out of both figures: it has no single sector, so calling it one inflates that sector, and calling it diversification inflates that instead. A holding whose classification is genuinely missing is left out too, and tracked separately. The share of the book those two buckets cover travels as its own number, so a book that is half funds cannot report a clean-looking split on the other half.
A worked example
An eight-holding book, valued this morning:
- Semiconductor name, $18,000 · technology
- Large-cap software name, $14,000 · technology
- Consumer hardware name, $9,000 · technology
- Second semiconductor name, $7,000 · technology
- Enterprise software name, $4,000 · technology
- Pharmaceutical name, $8,000 · health care
- Money-center bank, $6,000 · financials
- Integrated oil name, $4,000 · energy
The book total is $70,000. The five technology positions add to $18,000 + $14,000 + $9,000 + $7,000 + $4,000 = $52,000, and 52,000 / 70,000 = 0.743, so 74.3% of the book is technology. Health care is 11.4%, financials 8.6%, energy 5.7%. Four sectors are represented.
Read both numbers against the eight-holding row below. The reference band for the largest sector is 33.0% to 48.1%, limit 57.3%; this book is at 74.3%, well past it. Its four sectors sit exactly on the floor of 4, below the middle half of 5 to 6.
That comparison says the book is more concentrated in one sector than an eight-name book assembled with no thought about sector at all, by a wide margin. It does not say the sector is a bad one, that anything is mispriced, or that something is about to happen. Owning three of the eight outside technology felt like diversification while the arithmetic ran the other way, which is the ordinary case rather than an unusual one.
What counts as concentrated, by holding count
No single percentage means concentrated, because the holding count settles much of the arithmetic before you make a decision. A two-name book has a largest sector of at least 50% and often 100%. A thirty-name book cannot easily get there. One fixed threshold would tell every small book it had failed while saying nothing about the book, so Clavix measures a band per holding count.
The band is the middle half of a reference population, the 25th to the 75th percentile. The limit is the 90th percentile. For the sector count, where more is better, the limit is instead a floor read from the 10th percentile. To see the five dimensions Clavix already scores on a name you own, open it in the stock risk directory. To grade a whole book, the free portfolio grader takes three to twenty tickers and needs no account.
Sector reference bands by holding count
Each cell shows the ordinary band on the first line and, underneath, the point past which a book leaves it. For sectors represented, more is better, so that second line is a floor rather than a ceiling.
| Holdings | Largest sector | Sectors represented |
|---|---|---|
| 2 | 61.9–88.9over 100.0 | 2–2under 1 |
| 3 | 50.9–73.5over 85.9 | 2–3under 2 |
| 5 | 40.0–58.5over 70.0 | 3–4under 3 |
| 8 | 33.0–48.1over 57.3 | 5–6under 4 |
| 10 | 30.3–44.1over 52.6 | 5–7under 5 |
| 15 | 26.6–38.1over 45.3 | 7–8under 6 |
| 20 | 24.7–34.8over 41.1 | 8–9under 7 |
| 30 | 22.6–31.0over 36.2 | 9–10under 8 |
Source: the Clavix concentration band model, version concentration-bands-v1. Reference population: 20,000 simulated books per holding count, drawn without replacement from the 1,000 classified single-stock tickers Clavix scores, each name carrying its real sector, weights drawn from a Dirichlet distribution at alpha 1.397 fitted to 33 real portfolio weight vectors. Band = 25th to 75th percentile. Limit = 90th percentile, except for sectors represented, where more is better and the limit is a floor read from the 10th percentile instead. The reference books are assembled without regard to sector. So the band is not what other Clavix users look like, and is never captioned that way. It is what a book of your size looks like when nobody was concentrating on purpose.
Because those reference books ignore sector entirely, their sector counts show what chance alone produces: a 10-name book picked with no thought lands at 5 to 7 sectors, a 30-name book at 9 to 10. Spreading across sectors is the default outcome of picking names, not an achievement.
Which inverts the usual reading. A reader with 10 holdings in 3 sectors is not merely undiversified. They are below the floor of what randomness produces, so the narrowness was manufactured, and that is true even when nobody decided to concentrate. Buying what you understand, or what your industry talks about, or what did well last year, produces a book tighter than a dartboard would, and the arithmetic is the only place it shows.
Why sector exposure hides
Sector labels genuinely disagree. Check your book on two sites and you can get two answers, because providers classify the same company differently and split at different levels. A payments company lands in technology or in financials. A car maker with a battery business lands in consumer discretionary or in industrials. Neither site is lying. There is no single official taxonomy, so a reader who checks twice concludes the measure is soft and stops measuring, when the right conclusion is that the measure is real and the label needs pinning down once.
Then there are funds. A fund carries its own label, and that label describes the fund, not the companies inside it. A broad market fund is not a sector, and yet a book of one broad fund plus four semiconductor names is more exposed to semiconductors than the four positions alone suggest, because the fund is carrying more of them too. Ticker-level arithmetic cannot see through the wrapper, which is why funds are excluded from the figures rather than assigned a sector.
The third reason is the one nothing labels at all. A book can sit across ten names and four sectors and still ride on one end market. Ten suppliers to the same customer. A machinery name, a chemicals name and a rail name that all get paid when construction is busy. A bank, an insurer and a homebuilder that all move on the same rate decision. The sector column says four, and one decision in one industry moves the whole book. Sector exposure is the measurable part of that risk, not the whole of it.
Underneath all three, nobody sees their own weights. Brokerage screens sort by position, by day change, by gain, and very few show a value-weighted sector split. The 74.3% above looked like eight names, three of them outside technology.
How Clavix reads this
Two different measurements share the word sector, and keeping them apart is the most useful thing on this page. Sector resilience is a condition read: how the sectors you own are standing up against the broad market right now. Sector exposure is a share of your money: how much of the book sits in one sector. A book can be heavily exposed to a sector that is doing well, or barely exposed to one under real pressure. They are not the same number and neither substitutes for the other.
Clavix ships the first one today. Sector resilience is one of the four weighted dimensions behind every grade, alongside price stability, macro resilience and news sentiment, and it reads how a stock's sector is standing up relative to the broad market. Financial health is scored and shown as a fifth read, and is not weighted into the grade. A strong company in a sector under pressure inherits some of that pressure. The full construction is in the grading methodology, and what the product does and does not do is on the about page.
You can see it reach a portfolio grade right now, though not as a figure of its own. The first of the three layers behind that grade is asset quality, which is each holding's own grade weighted by how much of the book it is, and sector resilience is one of the readings inside those holding grades. So a book sitting in sectors that are struggling grades lower for it, weighted by what you actually own rather than averaged flat. What the grader will not do is break that back out: its results name the weakest of the four layers, not the weakest of the five per-ticker readings.
The read itself is taken against a proxy tape per sector rather than a survey: XLK for technology, XLV for health care, XLF for financials, XLE for energy, XLY for consumer discretionary, XLP for consumer staples, plus finer industry tapes where a liquid one exists, including SOXX for semiconductors, IBB for biotechnology, KBE for banking, KIE for insurance and XRT for retail. A semiconductor name is read against semiconductors, not against technology as a whole.
One honest caveat about the labels: the sector values Clavix stores are a mix of GICS sectors and finer industry-group labels, things like Machinery, Insurance and Aerospace and Defense, rather than one clean taxonomy. Both kinds are mapped, to a proxy tape and to a parent GICS sector, so every stored label resolves. It is still a mix, and worth knowing when you compare a Clavix sector read against a number from somewhere else.
What the grader does not do is compute your sector exposure. It returns no largest-sector share and no sector count. The bands above are a versioned, deployed measurement model rather than a screen you can open, which is exactly why the arithmetic is written out in full here: with the six steps in section two and the table above, you can measure your own book this afternoon and read the answer against a real reference population.
Check your own portfolio
Sector exposure is arithmetic you can do yourself with the table above; sector resilience is the read Clavix already runs on every name you own, and it reaches your portfolio grade through the asset-quality layer, weighted by what you actually hold.
The free Clavix grader
- Takes three to twenty holdings, entered by ticker and either a share count or a dollar amount. Below three it declines to grade rather than grading thinly, because two of the four things it measures describe how holdings behave together.
- Returns one A+ to F grade for the whole book, built from three layers: asset quality, less a penalty for how much of the money sits in the largest names, less a penalty for how much those names move together.
- Measures a fourth, stability, from how the book has actually behaved, and reports it beside the grade rather than inside it.
- Names the weakest of those four layers. It does not break the grade back out into the five per-ticker dimensions; for those, open a name in the stock risk directory.
- Weights by position value when you give share counts or amounts, and equally when you give neither. It tells you which it used.
- Names any ticker it does not cover and leaves it out, rather than dropping it quietly.
- No account, no email, no brokerage connection. Your tickers are sent to be scored and are never stored: no record of your holdings is kept.
Frequently asked questions
Is 40% of my portfolio in one sector too much?
It depends on how many names you own. In the Clavix reference set, a book of 10 holdings assembled with no regard to sector lands between 30.3% and 44.1% in its largest sector, so 40% is inside ordinary chance. The same 40% on a 30-holding book sits above the 36.2% limit, because more names normally spread the weight further.
How many sectors does a diversified portfolio usually cover?
More than most people expect, because random selection already spreads a book around. Clavix measured simulated books drawn without regard to sector: 5 holdings land at 3 to 4 sectors, 10 holdings at 5 to 7, and 30 holdings at 9 to 10. A 10-name book sitting at 3 sectors is therefore more concentrated than chance, not merely less diversified.
How do I calculate the sector exposure of my portfolio?
Price every holding, add the values for a book total, tag each holding with its sector, then sum the values by sector and divide each sum by the total. The largest of those percentages is your largest-sector share. Counting the distinct sectors gives the second number. Funds have no single sector, so Clavix leaves them out of both figures rather than guessing.
Does Clavix show my sector exposure?
Not today. The free grader at getclavix.com/grade returns one grade for the whole book, and the first of the three layers behind it is asset quality, which is each holding's own grade weighted by how much of the book it is. Sector resilience is one of the readings inside those holding grades, so how your sectors are faring versus the market does reach the number. What the grader does not compute is what share of your money sits in any one sector. The reference bands on this page let you work that figure out yourself.
What is the difference between sector exposure and sector resilience?
Sector exposure is a share of your money: how much of the book sits in one part of the economy. Sector resilience is a condition read: how the sectors you own are standing up against the broad market right now. A book can be heavily exposed to a sector that is doing well, or lightly exposed to one under pressure. They are two different numbers.
Do ETFs count toward my sector exposure?
A broad fund has no single sector, so counting it as one would overstate that sector, and counting it as diversification would overstate that too. Clavix excludes funds from both the largest-sector figure and the sector count, and keeps the share of the book they cover as a separate number. A single-sector fund is a different case: its weight really does sit in that sector.
For educational purposes only. This page explains how a risk measure is calculated; it is not investment advice, not a recommendation about any security, and not a prediction of return. Clavix is not a broker-dealer or a registered investment adviser. Consider consulting a licensed professional before making investment decisions.