A thematic ETF is sold as a way to get exposure to one idea, but the holdings often overlap with the S&P 500 by a wide margin. Across 380 funds with the relevant data, the typical thematic ETF holds 30% of its weight in stocks the S&P 500 already contains. That is a median, so half of funds sit above this number and half below. At the high end, 74 of the 380 funds have more than sixty percent of their weight in index names, meaning the theme is doing less work than the label suggests for those portfolios.
The pattern is uneven across themes. Energy security and critical technology shows a median of 86% already in the S&P 500, and AI infrastructure and chips sits at 63%, alongside Digital infrastructure and data centers and Semiconductors at 62%. At the other end, Cannabis and Coal both show 0%, and Silver miners and Gold miners sit at 2% and 5%. Active share, the share of a fund's portfolio that differs from the index, mirrors this: Metaverse and immersive tech has a median active share of 77%, the lowest in the table, while several themes, including Gold miners, Nuclear and uranium, Water, Space, Miners and metals, Rare earth and critical materials, Lithium and battery metals, Agriculture, Cannabis, and Timber and forestry, show 100%.
Fees do not adjust for this. Across 54 themes and 406 funds, the median fee is 0.60%. When the fee is measured only against the part of each fund that differs from the S&P 500, the median fee for that difference is also 0.60%. Some themes show a gap between the two numbers. Artificial intelligence carries a fee of 0.70% against a fee-for-the-difference of 0.80%, and AI infrastructure and chips shows the same pattern, 0.70% against 0.80%. Biotech runs the other way, with a fee of 0.50% against 0.30% for the difference.
Overlap between individual funds is also visible in the data. Among the pairs tracked, 136 hold portfolios that are more than half identical by weight, and the summary notes that holding both is close to holding one of them twice. The largest overlap in the pairs table is PDBA and EVMT in Agriculture at 98%, followed by AUAU and GDX in Gold miners at 83% and SOXQ and SOXX in Semiconductors at 82%. Fees within these pairs sometimes differ, as with FTXL and SOXX, which overlap 77% but carry fees of 0.60% and 0.33%.
One-year returns varied widely by theme. Semiconductors funds beat the S&P 500 in 9 of 9 cases with a median total return of +102.3%, while Defense funds beat the index in 0 of 14 cases with a median return of +1.9%. Nuclear and uranium showed a median return of −14.8%, and Internet and e-commerce showed −14.1%.
Readers can check any fund's in-index weight, active share, and fee-for-the-difference numbers, along with the overlap percentage for specific fund pairs, on the live desk.