Thematic exchange-traded funds are often sold as a way to get exposure that a plain S&P 500 tracker does not already give. The data suggest the separation is partial. Across 388 funds with holdings data, the median thematic fund has 32% of its weight in stocks the S&P 500 already holds. Seventy-two of those 388 funds are more than sixty percent index names, meaning a majority of their portfolio by weight overlaps with the S&P 500 before any theme-specific stock is counted.
The overlap varies widely by theme. Energy security and critical technology has a median of 85% of its weight already in the S&P 500, the highest of the themes shown, alongside a median active share of 95%, the share of the portfolio that differs from the index by weight. AI infrastructure and chips (63%) and Semiconductors (65%) also sit at the high end of in-index weight despite carrying high active share numbers, since active share and in-index weight measure different things: a stock can be in both the S&P 500 and a theme fund, and the theme fund can still be very different from the index overall in its combined weighting pattern. At the other end, Gold miners, Silver miners, Cannabis and Coal show in-index weight at or near zero, meaning these funds hold almost nothing that the S&P 500 also holds.
Fees sit at a median of 0.60% across 415 funds and 54 themes. When the fee is measured only against the part of each portfolio that differs from the S&P 500, the median fee for that difference is also 0.60%. This number answers a narrower question: once the S&P 500-overlapping stocks are set aside, what is being paid for the remaining, distinct holdings. By theme, this adjusted fee ranges from 0.30% for Beauty and personal care up to 1.00% for Cooling and thermal management, with Semiconductors and Biotech near the low end at 0.40% and Space and AI infrastructure and chips near 0.80%.
The data also show that many thematic funds resemble each other as much as they resemble the index. Across all theme pairs examined, 126 pairs hold portfolios that are more than half identical by weight. The listed pairs include GII and IGF in Infrastructure at 97% weight overlap, IBB and IBBQ in Biotech at 86%, and several Semiconductor pairs such as SOXQ and SOXX at 83% and FTXL and SOXX at 78%. These pairs carry different fees despite the similarity in holdings: GII charges 0.40% against IGF's 0.37%, while IBB charges 0.44% against IBBQ's 0.19%.
One-year total returns varied by theme, from +64.5% in Semiconductors to −35.4% in Blockchain and crypto equities, with "beat the S&P 500" counts showing, for example, 9 of 9 Semiconductor funds and 0 of 14 Defense funds ahead of the index over the same one-year period.
Readers can look up any individual fund's in-index weight, active share, fee, fee on the difference, and one-year return, along with its theme classification, on ETFIQ's fund pages.