AI and chip stocks lose $1 trillion in four days
The world's 20 most valuable AI and semiconductor stocks shed more than $1 trillion in market value between 12 and 15 October. Rate expectations, the cost of financing the build-out and Chinese memory makers drove the selloff.
What happened
The second week of October was rough for AI stocks. The combined market value of the world's 20 most valuable AI and semiconductor companies fell by more than $1 trillion over four trading days. On Thursday SK Hynix dropped more than 10%, Samsung Electronics 8.7%, Advantest nearly 14% and ASML 6.6%.
The numbers
Nvidia lost the most, falling 5.3% in four sessions, about $291 billion. SK Hynix lost roughly $244 billion and Samsung roughly $237 billion. The memory trio of Samsung, SK Hynix and Micron accounted for about 40% of the total. The Philadelphia Semiconductor Index fell about 10% over six sessions, its longest slide since May 2025.
Why it fell
US inflation came in at 3.7% in September, above forecasts, reviving bets on another Fed hike in October. Higher rates hit companies valued on future growth hardest. Data centres are increasingly financed with debt, so rising rates raise the cost of the build-out. Added capacity from Chinese memory makers also raised fears of future price pressure.
Who it affects
The IMF warned the same week that an AI correction could have global consequences. Even TSMC's strong results did not stop its shares from falling. UBS described the move as a reset of expectations rather than a collapse in AI investment.
Is this like 2025
The chip index's previous longest losing streak came in May 2025, when rate and trade worries also triggered a selloff that gave way to new highs within months. The difference now is scale. Big Tech spends hundreds of billions a year on AI, and a growing share is financed with debt, so every rise in rates makes the investment itself more expensive. Demand shows no sign of breaking: TSMC reported record profit the same week and raised its outlook. The market is questioning the financing bill, not the demand.
What comes next
The Fed meets on 27-28 October. Big Tech third-quarter results at the end of the month, especially capital spending guidance, will show whether chip demand holds.
What it means for your business
A market selloff does not mean your AI tools disappear tomorrow. Build workflows that can switch between two model providers, prefer monthly plans while prices reset, time hardware purchases carefully because memory prices swing, and if you invest, check how much of your portfolio sits in tech.