Published Oct 16, 2026, 4:39 PM ET
Today's move, what drove it, and what the available information cannot explain.
Capitalisation weighted, so a move in the largest companies moves it more than a move in the smallest.
Every Nasdaq listing, weighted by capitalisation and heavy in technology.
Thirty names weighted by price rather than by capitalisation, so it can disagree with the S&P for arithmetic reasons alone.
Small capitalisation names. Read against the S&P, it is the size half of how broad a day was.
The same five hundred companies weighted equally, so the largest names count no more than the smallest. Read against the cap-weighted index, the gap is how much of the day belonged to the biggest companies.
The equal-weighted index outran the cap-weighted one, so the session was broader than the headline index makes it look.
13%
1 of 8 tracked indices above their 50-day average
Counted over ^GSPC, ^IXIC, ^DJI, ^RUT, ^FTSE, ^N225, ^GDAXI, 000001.SS. This is a reading across whole market indices, not a count of the companies inside any one of them.
CNN's own index, stored at the close. Context for whether sentiment confirms the tape or contradicts it.
Expected thirty day volatility from S&P 500 options. Rising with the index is the contradiction worth seeing.
Same day news describes an AI stock selloff tied directly to CoreWeave distress and spending concerns.
News event dated 2026-10-16, CNBC Top News: AI stock selloff deepens amid CoreWeave distress and spending concerns
Moved 11.9%, at or above the 3% floor for this strip
Prior day 8-K disclosed departure of directors and officer compensatory arrangement changes ahead of the drop.
Headline dated 2026-10-15: Super Micro Computer filed an 8-K (items 5.02 and 9.01): Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers: Compensatory Arrangements of Certain Officers; Financial Statements and Exhibits
Moved 9.9%, at or above the 3% floor for this strip
Same day 8-K regulation FD and other events disclosure filed on the day of the decline.
Headline dated 2026-10-16: Strategy filed an 8-K (items 7.01 and 8.01): Regulation FD Disclosure; Other Events
Moved 9.6%, at or above the 3% floor for this strip
The evidence read for this company over the 7 days before the session was its own SEC filings, its stored corporate actions, the headline feed collected for its ticker, the clustered news events this system collects every two hours across every category and the same events that name the company in their own text. Rows naming this company were read inside that window and none of them was resolved to this session's move.
Moved 7.2%, at or above the 3% floor for this strip
Same day news on Nvidia's new Arm based laptop chips raises competitive concerns for AMD.
News event dated 2026-10-16, The Verge: Nvidia's new RTX Spark N1X laptops deliver high performance with Arm-based architecture
Moved 6.0%, at or above the 3% floor for this strip
The evidence read for this company over the 7 days before the session was its own SEC filings, its stored corporate actions, the headline feed collected for its ticker, the clustered news events this system collects every two hours across every category and the same events that name the company in their own text. Rows naming this company were read inside that window and none of them was resolved to this session's move.
Moved 5.8%, at or above the 3% floor for this strip
The evidence read for this company over the 7 days before the session was its own SEC filings, its stored corporate actions, the headline feed collected for its ticker, the clustered news events this system collects every two hours across every category and the same events that name the company in their own text. None of them holds a row for this company inside that window.
Moved 4.9%, at or above the 3% floor for this strip
Built in code from the movers whose evidence did not resolve, so no written summary can shorten this list.
The S&P 500 fell 1.09% while the equal weight fund fell only 0.42%, a gap of 0.67 points, pointing to losses more concentrated than the headline index alone suggests.
Nasdaq fell 2.15% versus Dow down only 0.34% and Russell 2000 down 1.66%, a split suggesting large cap growth names bore a heavier decline than the broader market.
Sector returns ranged from Energy up 2.52% to Technology down 3.02%, a wide spread beneath a headline index decline of just over one percent, pointing to defensive rotation.
Participation fell to 1 of 8 tracked indices above their 50-day average from 4 of 8 the prior session, a sharp drop in breadth alongside the index decline.
One session, from the stored closes of the eleven sector ETFs. Each bar is scaled against the widest move of the day, so the shape is the spread and not an absolute size.