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 55 of 244 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%.
94 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 give investors exposure to a specific idea, but the latest holdings filings show how much of that exposure already sits inside a plain S&P 500 tracker. Across 244 funds, the typical thematic ETF holds 32% of its weight in stocks that are already in the S&P 500. At the extreme, 55 of those 244 funds carry more than sixty percent of their weight in index names, meaning the "theme" is, by weight, mostly index.
The overlap varies a great deal by theme. Semiconductors, the largest theme by assets with 9 funds, shows a median of 81% of weight already in the S&P 500 and a median active share of 82%, meaning most of the portfolio's weight duplicates the index while the number of distinct names still runs high. Digital infrastructure and data centers, with 8 funds, sits at 64% in the S&P 500. At the other end, several themes show very little S&P 500 overlap: electric vehicles and batteries at 9%, clean energy at 10%, space at 14%, and cannabis at 0%. Active share, a separate measure of how different the actual portfolio is from the index by weight, runs high across almost every theme, often in the 90s or higher, even where the in-index share is also elevated, since active share and in-index weight capture different things: one counts what's shared, the other what differs.
Fees sit alongside this. Across 27 themes and 285 funds, the median fee is 0.60%. When that fee is measured only against the part of a fund's portfolio that differs from the S&P 500, the median fee for the difference is also 0.60%, unchanged in the aggregate. By theme, fees for the difference range from 0.40% in semiconductors and cloud and software up to 0.80% in space, cannabis, fintech and digital payments, and metaverse and immersive tech.
One-year total returns and win rates against the S&P 500 vary widely and do not move in lockstep with index overlap. Semiconductors funds beat the S&P 500 in 9 of 9 cases with a median one-year return of +105.7%. Defense funds, with much lower in-index weight at 35%, beat the S&P 500 in 0 of 11 cases despite a positive median return of +8.6%. Internet and e-commerce, gaming, esports and betting, and fintech and digital payments each show 0 wins against the S&P 500 alongside negative median returns.
Separately from index overlap, some thematic funds overlap heavily with each other. The tables list 94 pairs of funds whose portfolios are more than half identical by weight; holding both funds in such a pair is close to holding one of them twice. Among the listed pairs, SOXQ and SOXX show an 83% weight overlap in semiconductors, with fees of 0.19% and 0.33% respectively, and SPAM and PSWD show a 76% overlap in cybersecurity, with fees of 0.35% and 0.20%.
On the live desk, a reader can look up any individual fund's current in-index weight, active share, fee, and one-year return, along with the full list of overlapping pairs beyond those shown here.
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 | +105.7% |
| Defense | 19 | 35% | 98% | 0.50% | 0.50% | 0 of 11 | +8.6% |
| Artificial intelligence | 47 | 60% | 81% | 0.70% | 0.80% | 21 of 26 | +36.5% |
| Electrification and the grid | 14 | 27% | 99% | 0.60% | 0.60% | 9 of 11 | +66.7% |
| Cybersecurity | 7 | 33% | 99% | 0.50% | 0.50% | 6 of 7 | +26.3% |
| Infrastructure | 9 | 33% | 97% | 0.50% | 0.50% | 0 of 7 | +17.0% |
| Cloud and software | 8 | 45% | 92% | 0.40% | 0.40% | 2 of 7 | +7.5% |
| Nuclear and uranium | 9 | 15% | 100% | 0.70% | 0.70% | 0 of 8 | +9.3% |
| Broad innovation and megatrends | 31 | 51% | 86% | 0.50% | 0.60% | 15 of 29 | +20.0% |
| Internet and e-commerce | 14 | 29% | 95% | 0.70% | 0.70% | 0 of 14 | −13.4% |
| Robotics and automation | 12 | 17% | 94% | 0.70% | 0.70% | 6 of 8 | +22.5% |
| Clean energy | 17 | 10% | 99% | 0.60% | 0.60% | 10 of 15 | +26.5% |
| Quantum computing | 3 | 36% | 84% | 0.50% | 0.50% | 1 of 1 | +54.0% |
| Water | 7 | 38% | 100% | 0.50% | 0.60% | 0 of 6 | −1.9% |
| Space | 8 | 14% | 99% | 0.80% | 0.80% | 2 of 2 | +24.9% |
| Digital infrastructure and data centers | 8 | 64% | 94% | 0.50% | 0.50% | 5 of 7 | +36.8% |
| Blockchain and crypto equities | 12 | 18% | 98% | 0.60% | 0.70% | 2 of 12 | +9.1% |
| Electric vehicles and batteries | 13 | 9% | 98% | 0.50% | 0.50% | 7 of 11 | +33.2% |
| Genomics and biotech innovation | 4 | 18% | 98% | 0.50% | 0.50% | 3 of 4 | +71.0% |
| Cannabis | 4 | 0% | 100% | 0.80% | 0.80% | 0 of 4 | −1.7% |
| Food and agriculture | 6 | 36% | 100% | 0.60% | 0.50% | 4 of 5 | +21.1% |
| Fintech and digital payments | 4 | 42% | 94% | 0.70% | 0.80% | 0 of 4 | −17.0% |
| Gaming, esports and betting | 7 | 16% | 100% | 0.60% | 0.60% | 0 of 7 | −17.9% |
| Metaverse and immersive tech | 4 | 46% | 78% | 0.60% | 0.80% | 1 of 4 | +11.7% |
| Healthcare innovation and GLP-1 | 5 | 27% | 99% | 0.50% | 0.60% | 3 of 5 | +20.5% |
| Longevity and aging | 1 | 45% | 95% | 0.50% | 0.50% | 0 of 1 | +10.2% |
| Pets and consumer themes | 3 | 18% | 99% | 0.50% | 0.50% | 0 of 2 | −16.7% |
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 | 82% | Semiconductors | 0.40% | 0.35% |
| FTXL and SOXQ | 78% | Semiconductors | 0.60% | 0.19% |
| SPAM and PSWD | 76% | Cybersecurity | 0.35% | 0.20% |
| SMH and SOXX | 74% | Semiconductors | 0.35% | 0.33% |
| BUG and WCBR | 74% | Cybersecurity | 0.50% | 0.45% |
| BKCH and DAPP | 72% | Blockchain and crypto equities | 0.50% | 0.52% |
| 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% |
| BITQ and DAPP | 71% | Blockchain and crypto equities | 0.85% | 0.52% |
| BITQ and BKCH | 71% | Blockchain and crypto equities | 0.85% | 0.50% |
| SHOC and SOXX | 70% | Semiconductors | 0.40% | 0.33% |
| HERO and NERD | 70% | Gaming, esports and betting | 0.50% | 0.50% |
| FIW and PHO | 70% | Water | 0.50% | 0.59% |
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 9, 2026. https://etfiq.com/research/2026-09-09/themes-index Free to use with attribution; the underlying file is at https://etfiq.com/data/thematic.json.