Chip stocks have lost at least a trillion dollars over six sessions — and the contagion is spreading to Seoul
The Philadelphia Semiconductor Index (SOX) closed on October 14, 2026, down 4.3% — a sixth straight down day and the longest losing streak since May 2025. The next day, both the KOSPI and KOSDAQ triggered circuit breakers. Behind the numbers lie three converging pressures: hotter rate fears, doubts about AI revenues — and a Chinese memory competitor that upended sentiment across the entire sector.
What happened
At Wednesday's US market close on October 14, the Philadelphia Semiconductor Index fell 4.3% in a single session. It was the sixth consecutive daily decline and a cumulative drop of more than 10% since the streak began — the longest run of losses since May 2025 (BigGo Finance). CNN Business measured the decline at around 12% over the past week (CNN).
The selloff dragged the whole market with it: the S&P 500 fell 1.11% and the Nasdaq Composite 1.88%, both logging their worst day since July. Individual stocks fell far harder: Marvell 8.7%, Oracle 8.8%, Dell 11.3% and Nvidia 3.2%, according to CNN Business.
According to an estimate attributed to Bloomberg, the index's companies have lost roughly $1.6 trillion in combined market value over the six sessions — a figure BigGo compares with Turkey's entire GDP in 2025. But caution is warranted here: Yahoo Finance/Stocktwits cites a different Bloomberg report speaking of "more than $1 trillion." Both figures are attributed to Bloomberg, but they do not agree, and the gap — up to $600 billion — is too large to wave away as rounding. The safe statement is that the losses measure at least $1 trillion.
The contagion spreads to Asia
On Thursday, October 15, it was Asia's turn. According to Korea Exchange, the KOSPI opened 5.59% lower at 5,673.01, before trading was suspended at 5,527.12, a fall of 8.02%. The KOSDAQ also triggered a circuit breaker, with trading halted at 757.81 (Korea Times via MSN).
The sources describe the session's course differently: BigGo reports that the KOSPI closed down 7.57% after an intraday fall of more than 9%, while the Korea Times report has the suspension at −8.02%. It is therefore unclear whether trading resumed and closed lower, or whether the figures refer to different points in the session. We report both versions rather than smoothing over the disagreement.
The Korean memory giants took the worst damage: Samsung Electronics fell 9.48% and SK Hynix 11.06%, according to BigGo, and both stocks have now fallen for seven straight sessions.
Driver one: rates
The immediate trigger was the September US consumer price inflation figure, which came in at 3.7% year over year — above the consensus estimate of 3.6%. According to the CME FedWatch Tool, market pricing of a rate hike this month rose from 22% to 37% (Korea Times, citing CME).
Why does this hit AI hardware so hard? The answer lies in how the buildout is financed. Data centres, GPU clusters and power and cooling infrastructure are capital-intensive projects often carried on debt, and the value of the revenue streams they are meant to generate many years out depends directly on the level of interest rates. When markets begin pricing in higher rates rather than cuts, the present value of all those future AI revenues shrinks — and the stocks building them are exposed more than the rest of the market.
CoreWeave is the concrete example. The company, a so-called "neocloud" with an Nvidia backstop that rents computing power to the AI boom, plunged 15.5% on Wednesday after commentators highlighted a sharp rise in the company's bond yields (CNN). That is exactly the mechanism the Broadcom chief warned about.
Driver two: doubts about the revenues
According to a Guardian report relayed by BigGo Finance, dated October 9, OpenAI has now cut its revenue forecast for the AI business this year to $50 billion, from a previous $70 billion. The figure has not been confirmed by the company itself and should be read as secondary reporting — but in a market that has priced in aggressive growth trajectories, the news alone is enough to move capital.
In the same category is a JPMorgan analysis relayed by BigGo, which projects that growth in global cloud capital spending will fall from 97% in 2026 to 0% in 2029. This too rests solely on BigGo's account and is not confirmed in other sources. But the logic in both is the same: if revenue growth does not keep pace, capex must slow, and then the foundation under today's chip-sector valuations collapses.
Driver three: capital becomes the scarce resource
At a conference in Singapore, Broadcom chief Hock Tan warned that access to capital — rather than a shortage of chips or memory — could become the biggest constraint on further AI expansion. According to Yahoo Finance/Stocktwits, he compared parts of the speculative AI investment to casino gambling (Yahoo Finance).
It is worth noting who is saying it: Tan runs a company that profits from the AI boom, and the warning came on Monday, before the worst of the downturn. This article has only one basis for the claim that Intel's chief executive issued similar warnings on the same occasion, and that information is unconfirmed, so we leave it aside.
The CXMT factor: Chinese memory progress
The third pressure comes from the competition side. ChangXin Memory Technologies (CXMT), a Chinese memory company not listed in the US, reported progress on a denser memory-cell design, and the company is reportedly planning a product for AI data centres later this year (24/7 Wall St.). BigGo's rendering of the announcement's details appears incomplete, so open questions remain about the product's specifications and launch timing.
Even so, the market reaction was clear — and especially striking where it should not have hit directly: SanDisk, which does not produce DRAM, fell 6%, and storage rival Seagate lost 4% in the same selloff (24/7 Wall St.). The market thus priced CXMT in as a threat to the entire storage and memory segment, not just the DRAM market where the company actually competes with Samsung and SK Hynix. For Korean memory stocks, already sitting on seven down days, it was pure fuel on the fire.
Recalibration or turning point?
Not everyone reads the selloff as a verdict on the technology. Ulrike Hoffmann-Burchardi, chief investment officer for the Americas and global head of equities at UBS Global Wealth Management, described the decline this way: "More a recalibration of expectations than a fundamental break in the AI investment story" (Yahoo Finance).
That is the central open question after this week: Is this a healthy repricing of a sector that has run too hot, or the beginning of something structural? The evidence so far supports the description of three converging pressures — costlier capital, uncertain revenue forecasts, intensified competition — but provides no answer about the outcome. What could distinguish the two scenarios in the weeks ahead includes upcoming quarterly reports from the chip and cloud companies, whether the rate path actually tightens further, and above all whether capex guidance from the big hyperscalers is maintained or cut. Until then, the question remains open.