The semiconductor selloff that began Friday extended into Monday, May 18, 2026, with the four largest U.S. chip stocks all sliding between 3% and 7% intraday. The drawdown is small relative to the sector’s blistering 12-month run, but the math of how much the S&P 500 now leans on a handful of names has investors recalibrating risk.
The Monday tape: chips lead the downside
By midday Monday, Nvidia (NVDA) was off 4.4%, Broadcom (AVGO) was down 3.3%, Micron (MU) had dropped 6.6% and AMD (AMD) gave back 5.7%, according to stockanalysis.com. The moves came on top of a sharp Friday slide that had already pushed both major semiconductor ETFs — the VanEck Semiconductor ETF (SMH) and the iShares Semiconductor ETF (SOXX) — down close to 4% in a single session.
Yahoo Finance and Bloomberg both flagged the broader concern this week: chip stocks have been the dominant engine behind the S&P 500’s run to record highs, and some strategists are now openly describing the sector’s setup as “bubble-like euphoria”.
| Ticker | Company | Market Cap | Monday Move |
|---|---|---|---|
| NVDA | NVIDIA | $5.46T | −4.4% |
| AVGO | Broadcom | $2.01T | −3.3% |
| MU | Micron Technology | $817B | −6.6% |
| AMD | Advanced Micro Devices | $691B | −5.7% |
| Total | Top four U.S. chip stocks | $8.98T | — |
How concentrated has the index really become?
The S&P 500’s combined market capitalization sits at roughly $67.4 trillion across 502 listed share classes. The four chip names above represent about $9.0 trillion of that — roughly 13.3% of the index by market value. Nvidia alone, at $5.46 trillion, accounts for around 8.1% of the S&P 500’s float-adjusted weight, a single-stock concentration without modern precedent in the index’s history.
That concentration is even more pronounced inside the sector ETFs. As of Friday’s close on May 15, 2026, Nvidia carried a 17.6% weight inside the VanEck Semiconductor ETF (SMH), with Taiwan Semiconductor (TSM) at 9.7% and Broadcom at 7.3%. The equal-weighted iShares Semiconductor ETF (SOXX) is more diversified by design but still has Micron at 10.0%, AMD at 8.9% and Broadcom at 7.3% in its top three.
Why the “bubble” word is back
The rally that preceded this pullback is the reason it matters. SMH is up roughly 125% over the trailing 12 months; SOXX, slightly more balanced toward memory and equipment names, is up 138% over the same period. Returns of that magnitude in a single sector are historically rare and almost always invite questions about valuation, positioning and the durability of demand.
The bull case still rests on hyperscaler capex. Cloud and AI infrastructure spending from Microsoft, Alphabet, Amazon and Meta has continued to expand into 2026, and Nvidia reported in its Q4 FY26 release that data-center revenue reached $62.3 billion in the January-ending quarter, up 75% year over year. CEO Jensen Huang described “the agentic AI inflection point” as the next leg of demand growth.
The bear case is partly valuation, partly concentration: when one stock can move the entire index by a percentage point on an earnings reaction, index-level risk is no longer diversified the way investors typically assume. A Yahoo Finance round-up of sell-side notes this morning highlighted analysts re-running price targets ahead of Nvidia’s upcoming print, with the spread of views widening rather than narrowing.
The Nvidia print sits at the center of everything
The largest near-term catalyst is Nvidia’s first-quarter fiscal 2027 earnings report. Management’s prior guidance, issued alongside the Q4 FY26 release, calls for revenue of $78.0 billion plus or minus 2%, with GAAP gross margin around 74.9% and non-GAAP gross margin around 75.0%. Beating that range would put another rough $14–15 billion of incremental quarterly revenue into the data-center print versus the year-ago period; missing it — or, more importantly, guiding the next quarter below sell-side hopes — would almost certainly amplify the unwind that began Friday.
The set-up matters beyond Nvidia. Because of the concentration math, a 5% post-earnings move in NVDA mechanically swings the S&P 500 by roughly 40 basis points before anything else trades. That makes the print a market event rather than a single-stock event.
What to watch from here
- Breadth: If the S&P 500 holds up while chips give back, the rotation story stays intact. If chips drag the index down 1–2% on a single session, concentration risk is the story.
- Memory names: Micron’s 6.6% drop and Friday’s selloff in Korean memory peers (Samsung, SK Hynix) suggest the high-bandwidth memory trade — the most leveraged play on AI training capex — is taking the brunt of the de-risking.
- Forward guidance from Nvidia: The Q2 FY27 outlook will matter more than the Q1 number itself, since it is the first quarter that captures any change in hyperscaler order patterns.
- Volatility complex: Any meaningful pickup in the VIX or in single-stock implieds around earnings would be the cleanest sign that positioning has actually started to reset, not just the price.
Sources
- Nvidia — Q4 and Full Year Fiscal 2026 results, including Q1 FY27 outlook
- stockanalysis.com — S&P 500 constituent market caps and intraday moves
- stockanalysis.com — VanEck Semiconductor ETF (SMH) holdings and returns
- stockanalysis.com — iShares Semiconductor ETF (SOXX) holdings and returns
- Yahoo Finance — Stock market news, May 18, 2026 round-up
Disclosure: This article was produced with AI assistance and reviewed before publication. It is for informational purposes only and is not investment advice.