This was a rough week for US equities — the Nasdaq posted its worst weekly performance since June. If you're trading US indices through a prop firm funded account rather than a self-funded broker position, this is exactly the kind of week where the drawdown discipline covered in our managing risk guide actually gets tested.
Last Week: Inflation Shock, Then an AI Financing Scare
The week started on uneven footing, with chip weakness and mixed bank earnings keeping the S&P 500 roughly flat through Monday and Tuesday. Wednesday brought the real shock: a hotter-than-expected September US inflation report, which broadened price pressures across the economy and briefly reinforced bets that the Federal Reserve might raise rates again at its late-October meeting. The S&P 500 fell about 1% and the Nasdaq dropped nearly 1.9% on the day — snapping a remarkable 55-day streak without a single 1% daily decline in the S&P 500.
Thursday saw a partial recovery as Treasury yields cooled sharply, breathing life back into names outside the AI/tech trade. Then Friday hit hard: concerns about AI financing spread from CoreWeave to major technology names including Alphabet, compounding worries about expensive borrowing costs and a fresh jump in oil prices (Brent briefly touched $110 amid the Middle East escalation covered in our gold and oil weekly outlook). The Nasdaq fell 2.1% and the S&P 500 dropped 1.1% on the day alone.
For the week overall: the S&P 500 fell approximately 2.0% and the Nasdaq dropped 4.5% — its worst week since June. The Dow Jones Industrial Average, by contrast, actually gained roughly 0.7% for the week — a clear sign this was a rotation out of expensive AI and chip stocks rather than a broad market panic. The Philadelphia Semiconductor Index (SOX) fell for eight consecutive sessions, its longest losing streak since the 2008 financial crisis.
Why a Week Like This Matters for Prop Firm Traders Specifically
A 4.5% weekly drop in the Nasdaq is exactly the kind of move that can breach a daily or overall drawdown limit if a position was sized without this kind of volatility in mind. This is a useful real-world illustration of why our passing the challenge guide emphasizes sizing around your drawdown limit rather than around how fast you want to hit a profit target — a single volatile week like this one can undo weeks of careful progress if risk wasn't controlled from the start.
Outlook for This Week
The central question: was this a healthy rotation away from an overcrowded AI trade, or the start of something more serious? Market breadth actually improved during the week even as headline indices fell — payments names like Visa and Mastercard hit record highs even as chip stocks tumbled, suggesting money rotated rather than simply left the market.
Watch for: further developments in AI-financing concerns; whether the semiconductor sector's eight-day losing streak finds a floor; continued Fed rate expectations ahead of the late-October meeting (odds of a hike eased to around 28% by Friday); and oil prices, given their direct tie-in to this week's volatility — see our gold and oil weekly outlook for the full picture.
For the broader international perspective, see the global market view.
Frequently Asked Questions
Why did the Nasdaq fall so much more than the Dow this week?
The selloff was concentrated in AI-related and semiconductor stocks — the Nasdaq's heavy weighting toward technology names made it far more exposed than the Dow, which actually gained for the week as money rotated into other sectors.
What triggered Friday's sharp decline?
Concerns about AI financing spread from CoreWeave to major technology companies including Alphabet, compounding existing worries about high borrowing costs and a fresh jump in oil prices.
How should a week like this affect my prop firm trading?
A 4.5% weekly swing in the Nasdaq is a reminder to size index positions around your firm's specific daily and overall drawdown limits, not around how quickly you want to reach a profit target — see our managing risk on a prop account guide for the full approach.
This content reflects market information available as of October 18, 2026, and is for educational purposes only — it does not constitute financial or legal advice. It is not a recommendation to use any specific firm. Stock indices are highly volatile and can change significantly within hours; always check current prices before making any decision. This page should be refreshed or retired within approximately 7-10 days of publication.