Thematic ETFs are often described as a way to make a targeted bet away from the broad market. The data suggests that bet is frequently smaller than it looks. Across 391 funds with usable holdings data, the typical thematic fund holds 26% of its weight in stocks that are already in the S&P 500. 61 of those 391 funds are more than sixty percent overlapped with the index, meaning that for those funds, most of the portfolio is index exposure wrapped in a thematic label.
The picture varies by theme. Gold miners, internet and e-commerce, clean energy, agriculture, copper, rare earth and critical materials, lithium and battery metals, and a handful of smaller categories show a median of 0% to 7% in the S&P 500, with active share at or near 100%, meaning these portfolios look almost nothing like the index by weight. At the other end, energy security and critical technology shows a median 85% in the S&P 500 with 95% active share, AI infrastructure and chips shows 59% with 95% active share, and digital infrastructure and data centers shows 51% with 88% active share. Artificial intelligence, at 36 funds the second-largest theme by fund count, has a median 56% in the S&P 500 and 82% active share, among the lower active-share readings in the table.
Fees do not generally adjust for this. Across 54 themes and 419 funds, the median fee is 0.60%, and when that fee is measured only against the part of each portfolio that differs from the S&P 500, the median fee for the difference is also 0.60%. In other words, the price charged for the differentiated slice of these portfolios is, on a median basis, the same as the price charged for the whole thing.
Overlap also exists between pairs of funds, not just between funds and the index. The data shows 131 pairs of funds across all themes with portfolios more than half identical by weight, a point ETFIQ describes as holding both being close to holding one of them twice. The listed examples include GII and IGF in infrastructure at 97% weight overlap, with fees of 0.40% and 0.37%; IBB and IBBQ in biotech at 86% overlap, with fees of 0.44% and 0.19%; and three semiconductor pairings, SOXQ and SOXX at 83%, FTXL and SOXX at 78%, and SHOC and SMH at 77%, each carrying a different fee for the same theme. Space, gold miners, cybersecurity, and water also appear among the listed pairs.
Performance over the trailing year ranged widely by theme, from semiconductors at +84.4% median total return, where 9 of 9 funds beat the S&P 500, to blockchain and crypto equities at −30.1%, where 0 of 13 did. Readers can look up any individual fund's in-index weight, active share, fee, and the fee measured against only its differentiated holdings on ETFIQ's fund pages.