Most UK self-directed investors think about diversification in terms of geography. A "global" ETF and a "US" ETF and maybe a "UK" tracker, spread across an ISA and a SIPP, and the job is done. Geography is one axis, and a useful one. It is not the axis that explains most of how a portfolio actually behaves.
The axis that explains most of the day-to-day movement is sector. When the technology sector sells off, it does not matter that you hold a Vanguard fund and an iShares fund and a HSBC fund — if all three are sitting on top of the same handful of large US tech names, your portfolio drops together. This article walks through why sector exposure quietly compounds across passive funds, how to roll it up across an ISA, SIPP and GIA, and what tools surface the picture.
This is not financial advice. Past performance does not guarantee future returns. Consider speaking to an FCA-authorised financial adviser for personalised guidance.
Why sector matters more than most UK investors think
A handful of points worth being honest about up front.
Sector concentration is the dominant driver of correlated drawdowns in equity portfolios. When you read that "the market" fell three per cent on a particular day, what usually happened was that one or two sectors fell five to seven per cent and dragged the rest of the index with them. If your portfolio is over-weighted to those sectors, your drawdown will be deeper than the index print suggests.
Cap-weighted indices are sector-biased by construction. They allocate more weight to the largest companies, and the largest companies tend to cluster in whichever sector is currently in favour. In 2026, that is technology in the United States and financials plus consumer staples in the United Kingdom. Ten years ago it was financials in the US and energy and miners in the UK. The bias is not wrong — it is what cap-weighting does — but it means your sector mix is not chosen, it is inherited.
Sector rotation is not market timing. There is a tempting trap, especially in articles about sector exposure, to slide into "the technology sector looks expensive, sell tech and buy energy". That is timing dressed up as analysis, and it has a poor track record for self-directed investors. The useful framing is the opposite: knowing your sector mix lets you decide what risk you are taking, not which sector to chase.
How sector creeps in even with index ETFs
A standard "diversified" UK portfolio in 2026 might look something like this:
- A global tracker (
VWRL,SWDA, or similar) - A US tracker (
VUSA,CSPX) - A FTSE 100 tracker (
ISF,VUKE) - A small-cap or factor tilt (
WLDS,IUSA)
Three or four ETFs. Reasonable diversification on the brokerage screen. Now look at sector weights.
The S&P 500 in early 2026 sits around 30 to 32 per cent technology, depending on whose sector classification you use. If you include communication services (Alphabet, Meta) and Amazon — which sit in consumer discretionary by GICS but are tech businesses by economics — the "tech-adjacent" weight is closer to 40 per cent. A US tracker buys you that mix.
A global tracker like VWRL is roughly 60 to 65 per cent US, so its sector mix is largely the US sector mix diluted by twenty per cent of European, Japanese and emerging exposure. The technology weight in VWRL ends up around 23 to 25 per cent — lower than VUSA but still the single largest sector.
The FTSE 100, by contrast, has almost no technology weight. It is dominated by financials (banks, insurers, asset managers — about 21 per cent), consumer staples (about 17 per cent), energy (about 11 per cent) and healthcare (about 11 per cent). UK-only investors who think they are diversified by holding the FTSE are mostly diversified within "old economy" sectors.
Layer those funds together at typical UK retail weights and the sector picture is roughly:
| Sector | Typical UK retail mix | Notes |
|---|---|---|
| Technology | 22 - 28% | Heavily concentrated in five to seven US names |
| Financials | 14 - 18% | Mostly UK and US banks, insurers |
| Healthcare | 11 - 13% | Pharma giants dominate |
| Consumer Discretionary | 10 - 12% | Includes Amazon and Tesla in most classifications |
| Consumer Staples | 7 - 9% | Defensive — large UK weight from FTSE |
| Industrials | 8 - 10% | Diversified across regions |
| Energy | 4 - 6% | Largely UK and US oil majors |
| Communication Services | 6 - 8% | Alphabet and Meta dominate |
| Materials | 3 - 5% | Miners, chemicals |
| Utilities | 2 - 4% | Defensive |
| Real Estate | 2 - 4% | REITs |
Twenty-something per cent technology was not a deliberate decision. It is the residual of geography choices.
Rolling up sector across multiple ETFs
The mechanical job is straightforward in principle and tedious in practice. You need three pieces of information for every fund you own:
- The fund's current sector breakdown (issuer factsheet or KID).
- The fund's value in your portfolio (broker statement).
- A consistent sector classification (GICS, ICB, or the issuer's own).
Then for each sector, sum the product of (fund value × sector weight in fund) across all funds. Divide by total portfolio value. That gives you portfolio-level sector exposure.
The friction lives in three places:
- Different issuers use different classifications. Vanguard, iShares, Invesco, HSBC and SPDR do not all map sectors the same way. One vendor might count Amazon as consumer discretionary, another as internet retail under tech-adjacent. If you are rolling up by hand, you need to pick one classification and accept some translation error.
- Sector weights change. They drift quarterly with rebalances and corporate actions. A snapshot from January is wrong by April.
- Multi-asset funds are nested. A "60/40" fund holds equities (with a sector mix) and bonds (with no equity sector). You need to look through the equity sleeve only.
For a portfolio of three to five ETFs, an investor with patience can do this in a spreadsheet in an evening. For a portfolio of ten or more, automation pays for itself quickly.
When sector concentration becomes a problem
There is no number above which a sector weight is "too high". There is a sensible framework for thinking about it:
Compare to a global benchmark. The MSCI ACWI sector mix is the closest thing to a neutral starting point. If your tech weight is 30 per cent against ACWI's 24 per cent, you are taking a six-percentage-point active bet on tech, whether you intended to or not.
Look at single-name concentration inside the sector. A 25 per cent tech weight where Apple, Microsoft and Nvidia together are 40 per cent of that sector is meaningfully more concentrated than a 25 per cent tech weight spread across forty names. The headline sector number can hide the real risk.
Stress-test the drawdown. A simple back-of-envelope: if technology fell 30 per cent (the rough magnitude of the 2022 drawdown), and tech is 25 per cent of your portfolio, the direct hit is 7.5 per cent of total portfolio value. Plus correlated effects on related sectors. Is that a number you can sit with?
Match it to the wrapper and the time horizon. A 30 per cent tech weight in a SIPP that is twenty years from drawdown is a very different proposition from the same weight in a GIA you might tap in three years.
The honest answer to "what is a safe sector weight" is "the one you can live with through a thirty per cent drawdown without changing your mind". That number is different for everybody.
Tools that show sector breakdown
Three categories of tool exist, with different strengths.
Issuer factsheets and KIDs. Free, authoritative, but each fund in isolation. You can read the sector mix of any one ETF on the issuer site or in its Key Information Document. The work of rolling them up across multiple funds is yours.
justETF. A free European ETF database with sector breakdowns per fund and a portfolio builder that aggregates across selected ETFs. Useful for comparing two or three funds side by side. Less useful as a portfolio tracker because positions are entered manually and not reconciled with broker statements.
Sharesight. Tracks holdings at the security level and reports diversification by industry classification, including a breakdown across portfolios. The classification is built on the holdings the user inputs — for an ETF it treats the ETF itself as a single security, so the sector view does not look through to the underlying constituents. It is fine if your portfolio is mostly direct equities, less useful if it is mostly ETFs.
Invormed. Built specifically to look through ETFs to their constituents and roll sector exposure up across ISA, SIPP and GIA. The core promise: paste in your holdings, see what you actually own at the company and sector level, get an aggregated picture rather than a fund-by-fund one.
A sensible workflow for a UK investor today: use issuer factsheets or justETF to do a one-time sector audit on every ETF you hold, write the result down, then revisit twice a year. If that becomes more than you want to do by hand — or if you start adding factor and thematic funds where the sector mix is less predictable — a tool that does the look-through automatically saves real time.
A worked example
A UK investor holding £40,000 across four ETFs in a Stocks and Shares ISA, illustrative weights only:
VWRL(FTSE All-World) — £15,000VUSA(S&P 500) — £10,000ISF(FTSE 100) — £8,000WLDS(MSCI World Small Cap) — £7,000
Approximate sector breakdown of each (rounded):
| Sector | VWRL | VUSA | ISF | WLDS |
|---|---|---|---|---|
| Technology | 24% | 31% | 1% | 12% |
| Financials | 15% | 13% | 21% | 16% |
| Healthcare | 12% | 12% | 11% | 11% |
| Consumer Disc. | 11% | 11% | 7% | 13% |
| Industrials | 10% | 9% | 13% | 18% |
| Comm. Services | 7% | 8% | 4% | 4% |
| Consumer Staples | 7% | 6% | 17% | 5% |
| Energy | 4% | 4% | 11% | 4% |
| Materials | 4% | 2% | 8% | 7% |
| Utilities | 3% | 2% | 4% | 4% |
| Real Estate | 3% | 2% | 3% | 6% |
Weighted by holding size, the portfolio sector mix lands roughly:
- Technology: ~22.5%
- Financials: ~15.7%
- Healthcare: ~11.7%
- Consumer Discretionary: ~10.8%
- Industrials: ~11.0%
- Consumer Staples: ~8.4%
- Comm. Services: ~6.4%
- Energy: ~5.2%
- Materials: ~4.8%
- Utilities: ~2.9%
- Real Estate: ~3.2%
A reasonable result. Tech is the largest sector but not dominant. The FTSE 100 sleeve usefully tilts the picture toward financials, energy and consumer staples. The single-name look-through underneath would still show Apple, Microsoft and Nvidia as the largest individual exposures — but the sector mix is more balanced than a US-only investor would have.
The exercise is worth doing once per year. The result tells you whether the portfolio you actually own matches the portfolio you think you own.
FAQ
How do I see my sector exposure?
The free option: read the sector breakdown for each of your funds on the issuer factsheet or KID, then weight by your holdings in a spreadsheet. The faster option: use a portfolio tool that aggregates across funds — justETF for ETF-only portfolios, Sharesight for direct equities, Invormed for an ETF look-through view across ISA, SIPP and GIA together.
What's a "safe" tech-sector concentration?
There is no universal answer. A useful benchmark: the MSCI ACWI weight in technology (around 24 per cent in early 2026). Anything materially above that is an active bet, whether or not you meant to make it. The right number for you depends on your time horizon, your other risk tolerances, and your willingness to sit through a thirty per cent tech drawdown without selling.
Does Sharesight show sector breakdown?
Yes — Sharesight has a diversity-by-industry report that shows sector and industry exposure across the portfolio. The caveat is that Sharesight treats each ETF as a single security and does not look through to its underlying constituents. For a portfolio of direct equities the report is accurate. For a portfolio of ETFs, you only see "ETF" or the issuer-supplied classification of the fund itself, not the sectors of the companies inside the fund.
How does an MSCI World ETF break down by sector?
In early 2026, an MSCI World tracker is roughly: technology 25%, financials 15%, healthcare 12%, consumer discretionary 11%, industrials 10%, communication services 7%, consumer staples 7%, energy 4%, materials 4%, utilities 3%, real estate 3%. Weights drift quarterly with rebalancing — always check the current factsheet for the fund you actually hold.
Should I rebalance based on sector drift?
Mechanical rebalancing on geography or asset class has a strong evidence base. Mechanical rebalancing on sector has a weaker one — and slides quickly into market timing if you are not careful. A defensible middle ground: monitor sector drift as an information input, not a trigger. If a sector materially exceeds your comfort threshold (say, ten percentage points over your benchmark), revisit your fund choices rather than trying to time the rotation.
What tools show sector exposure across multiple ETFs?
justETF has a portfolio builder that aggregates sector exposure across selected ETFs (free, manual entry). Sharesight aggregates at the holding level but does not look through ETFs. Invormed is built specifically to look through ETFs to their constituents and roll up sector and single-name exposure across an ISA, SIPP and GIA in one view. For a one-off audit, justETF is enough; for ongoing tracking with broker integration, a dedicated tool is the cleaner path.
Want this kind of analysis on your real portfolio? Invormed is in early access — join the early-access waitlist and we will let you in as we open up.