Chipmakers reach unprecedented share of the benchmark
Semiconductor companies now account for a record 19.7% of the S&P 500, almost four times their weighting of around 5% in June 2020, according to Citadel Securities strategist Scott Rubner.
The sector’s influence has grown well beyond previous market peaks. Before the dotcom crash, semiconductor stocks represented just over 8% of the index, less than half their current share, highlighting the unprecedented concentration seen today.
Nvidia (NASDAQ:NVDA) has been the biggest contributor to the sector’s expanding index weight during the artificial intelligence boom. However, gains have broadened to include companies such as Broadcom (NASDAQ:AVGO), TSMC (NYSE:TSM), ASML (NASDAQ:ASML), AMD (NASDAQ:AMD), along with memory-chip makers Micron (NASDAQ:MU) and SanDisk (NASDAQ:SNDK), further increasing the sector’s dominance.
Passive investing continues to reinforce market concentration
Rubner said the concentration has become self-perpetuating. As semiconductor shares outperform, their weighting within the index rises, prompting passive investment funds to allocate even more capital to the same companies. That additional demand then supports further price gains and increases index weights again.
The trend has been amplified by exceptionally strong fund flows. According to Rubner’s analysis, exchange-traded funds attracted more than $1 trillion in inflows year-to-date through late June 2026, approximately 45% above the record pace seen during the same period last year.
Valuation concerns continue to build
Several market indicators are now signalling elevated valuations across the semiconductor sector.
According to a Reuters report published on June 30, Bank of America’s proprietary Bubble Risk Indicator reached 0.91 for the PHLX Semiconductor Sector and 0.82 for the Technology Select Sector on a scale where one represents extreme bubble-like conditions.
Meanwhile, LSEG head of earnings research Tajinder Dhillon noted that the S&P 500’s price-to-sales ratio has climbed to 3.22, well above its long-term average of 1.84. The widely followed Buffett Indicator, which compares total U.S. stock market capitalisation with gross domestic product, currently stands at 231.8%, indicating the market is “significantly overvalued.”
Investors remain divided over the AI-driven rally
Despite growing valuation concerns, not all market participants believe the concentration reflects a speculative bubble.
JJ Kinahan, head of retail expansion and alternative investment products at Cboe Global Markets, argued that semiconductor suppliers remain well positioned compared with the companies investing heavily in artificial intelligence infrastructure.
“The folks selling the picks and shovels are in incredibly good stead. Those buying them still have to prove that the billions and billions of dollars they’re spending is worth it.”
The debate over whether hyperscale AI spending will ultimately generate returns sufficient to justify current semiconductor valuations has become one of Wall Street’s central investment questions.
New-quarter fund flows could provide another boost
Recent market performance has hinted at an early rotation away from the largest technology names. During the previous week, the S&P 500 declined 1.94% while small- and mid-cap stocks outperformed, suggesting investors may be broadening their exposure beyond megacap chip companies.
Even so, Rubner highlighted July 1 as a potential near-term catalyst, with retirement contributions, target-date funds and systematic investment strategies expected to deploy fresh capital at the start of the new quarter.
Given semiconductor companies’ record weighting within the S&P 500, those inflows could provide additional support for the sector in the short term. Over a longer horizon, however, future interest-rate decisions under Federal Reserve Chair Kevin Warsh could alter valuation assumptions and encourage institutional investors to reduce exposure to the sector.
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