How much of a theme is already the index
By their latest holdings filings, the typical thematic ETF has 32% of its weight in stocks the S&P 500 already holds, and 56 of 245 funds are more than sixty percent index names.
Across 27 themes and 285 funds, the median fee is 0.60%; measured against only the part of each fund that differs from the S&P 500, the median fee for the difference is 0.60%.
88 pairs of funds hold portfolios that are more than half identical by weight; holding both is close to holding one of them twice.
Thematic ETFs are built to offer something the S&P 500 does not already hold. The data shows that promise is only partly kept. Across 245 funds, the typical thematic ETF has 32% of its weight in stocks the S&P 500 already holds, and 56 of those funds are more than sixty percent index names by weight. In other words, more than one in five thematic funds looks, for most of its portfolio, like a slice of the market it was meant to diverge from.
The overlap varies sharply by theme. Semiconductors, with nine funds, has a median of 81% of weight already in the S&P 500 and a median active share, the share of the portfolio that differs from the index, of 82%. Digital infrastructure and data centers, with eight funds, shows 64% in the S&P 500. At the other end, electric vehicles and batteries (13 funds) sits at 9% in the S&P 500, and cannabis (four funds) sits at 0%, with clean energy, space, and nuclear and uranium all in the teens. Active share, which measures how different the fund's holdings are from the index by weight, tracks this closely: themes with low S&P 500 overlap tend to show active share near or at 100%, meaning nearly the whole portfolio sits outside the index.
Fees do not adjust for this. The median fee across 285 funds and 27 themes is 0.60%, and when that fee is measured only against the part of each portfolio that actually differs from the S&P 500, the median fee for the difference is also 0.60%. Some themes show a wider gap between the two figures than others; artificial intelligence, for instance, carries a median fee of 0.70% and a median fee for the difference of 0.80%, while food and agriculture runs the other way, at 0.60% and 0.50%. For a theme like semiconductors, where 81% of the portfolio is already index weight, a 0.30% median fee applied to the whole fund becomes 0.40% once measured against just the non-index portion.
Overlap also shows up between funds themselves. Of all thematic pairs examined, 88 hold portfolios that are more than half identical by weight. The table of the most similar pairs includes SOXQ and SOXX at 83% weight overlap, both in semiconductors, with fees of 0.19% and 0.33%. SHOC and SMH overlap at 79%, and FTXL and SOXQ at 77%. Holding two such funds together does not double the exposure; it comes close to holding one fund twice, at two separate fee levels.
One-year returns varied widely across themes, from semiconductors at +98.0% to gaming, esports and betting at −17.9%, with beat-rates against the S&P 500 (the fraction of funds in a theme that outperformed it) ranging from 9 of 9 in semiconductors to 0 of several in defense, infrastructure, nuclear and uranium, internet and e-commerce, water, cannabis, fintech and digital payments, and gaming.
On the live desk, a reader can look up any individual fund's current in-index weight, active share, and fee for the difference, and check whether a specific pair of thematic ETFs they hold or are considering shows a high weight overlap.
By theme, largest assets first
| Theme | Funds | Median in the S&P 500 | Median active share | Median fee | Median fee for the difference | Beat the S&P 500, one year | Median total return, one year |
|---|---|---|---|---|---|---|---|
| Semiconductors | 9 | 81% | 82% | 0.30% | 0.40% | 9 of 9 | +98.0% |
| Defense | 19 | 35% | 98% | 0.50% | 0.50% | 0 of 11 | +4.9% |
| Artificial intelligence | 47 | 61% | 82% | 0.70% | 0.80% | 20 of 26 | +30.9% |
| Electrification and the grid | 14 | 29% | 99% | 0.60% | 0.60% | 8 of 11 | +54.6% |
| Cybersecurity | 7 | 28% | 99% | 0.50% | 0.50% | 5 of 7 | +24.9% |
| Infrastructure | 9 | 33% | 97% | 0.50% | 0.50% | 0 of 7 | +13.5% |
| Cloud and software | 8 | 45% | 92% | 0.40% | 0.40% | 1 of 7 | +7.5% |
| Nuclear and uranium | 9 | 15% | 100% | 0.70% | 0.70% | 0 of 8 | +1.9% |
| Broad innovation and megatrends | 31 | 51% | 86% | 0.50% | 0.60% | 14 of 29 | +17.6% |
| Internet and e-commerce | 14 | 29% | 95% | 0.70% | 0.70% | 0 of 14 | −13.7% |
| Robotics and automation | 12 | 18% | 94% | 0.70% | 0.70% | 5 of 8 | +21.1% |
| Clean energy | 17 | 10% | 99% | 0.60% | 0.60% | 9 of 15 | +22.1% |
| Quantum computing | 3 | 34% | 84% | 0.50% | 0.50% | 1 of 1 | +50.4% |
| Water | 7 | 38% | 100% | 0.60% | 0.60% | 0 of 6 | −4.9% |
| Space | 8 | 14% | 99% | 0.80% | 0.80% | 2 of 2 | +24.5% |
| Digital infrastructure and data centers | 8 | 64% | 94% | 0.50% | 0.50% | 5 of 7 | +34.5% |
| Blockchain and crypto equities | 12 | 19% | 98% | 0.60% | 0.60% | 1 of 12 | +3.1% |
| Electric vehicles and batteries | 13 | 9% | 98% | 0.50% | 0.50% | 7 of 11 | +33.1% |
| Genomics and biotech innovation | 4 | 21% | 98% | 0.50% | 0.50% | 3 of 4 | +67.8% |
| Cannabis | 4 | 0% | 100% | 0.80% | 0.80% | 0 of 4 | +5.4% |
| Food and agriculture | 6 | 35% | 100% | 0.60% | 0.50% | 4 of 5 | +20.4% |
| Fintech and digital payments | 4 | 37% | 94% | 0.70% | 0.80% | 0 of 4 | −16.7% |
| Gaming, esports and betting | 7 | 15% | 100% | 0.60% | 0.60% | 0 of 7 | −17.9% |
| Metaverse and immersive tech | 4 | 46% | 78% | 0.60% | 0.80% | 2 of 4 | +12.3% |
| Healthcare innovation and GLP-1 | 5 | 26% | 99% | 0.50% | 0.60% | 3 of 5 | +21.1% |
| Longevity and aging | 1 | 47% | 95% | 0.50% | 0.50% | 0 of 1 | +9.1% |
| Pets and consumer themes | 3 | 18% | 99% | 0.50% | 0.50% | 0 of 2 | −17.2% |
Same portfolio, two names: pairs more than half identical
| Pair | Weight overlap | Theme | Fee, first | Fee, second |
|---|---|---|---|---|
| SOXQ and SOXX | 83% | Semiconductors | 0.19% | 0.33% |
| SHOC and SMH | 79% | Semiconductors | 0.40% | 0.35% |
| FTXL and SOXQ | 77% | Semiconductors | 0.60% | 0.19% |
| SPAM and PSWD | 76% | Cybersecurity | 0.35% | 0.20% |
| BUG and WCBR | 74% | Cybersecurity | 0.50% | 0.45% |
| WGMI and MNRS | 71% | Blockchain and crypto equities | 0.75% | 0.59% |
| WEED and UX | 71% | Cannabis | 0.41% | 0.77% |
| WDEF and XDEF | 71% | Defense | 0.45% | 0.35% |
| BKCH and DAPP | 71% | Blockchain and crypto equities | 0.50% | 0.52% |
| SHOC and SOXX | 70% | Semiconductors | 0.40% | 0.33% |
| FIW and PHO | 70% | Water | 0.50% | 0.59% |
| ARKQ and ARKX | 69% | Robotics and automation | 0.75% | 0.75% |
| NERD and ESPO | 68% | Gaming, esports and betting | 0.50% | 0.55% |
| FTXL and SOXX | 68% | Semiconductors | 0.60% | 0.33% |
| SOXQ and SHOC | 67% | Semiconductors | 0.19% | 0.40% |
Method. Holdings from each fund’s latest public SEC N-PORT filing (issuer daily files for ARK and First Trust); in-index weight and active share computed by ETFIQ against the IVV and QQQM books; fees from prospectus XBRL; returns from Tiingo end-of-day prices with distributions reinvested. Themes are ETFIQ’s editorial taxonomy. Medians across funds. Data file: https://etfiq.com/data/thematic.json. Rebuilt every trading night. ETFIQ is an independent publisher and makes no recommendations. Standards
Cite this page. ETFIQ Research, How much of a theme is already the index, data as of Sep 11, 2026. https://etfiq.com/research/2026-09-11/themes-index Free to use with attribution; the underlying file is at https://etfiq.com/data/thematic.json.