Published Oct 21, 2026, 4:37 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 two moved together, so the session was not a story about the largest companies.
50%
4 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.
8-K disclosing results of operations and financial condition, consistent with a sharp earnings-related move.
Headline dated 2026-10-20: Super Micro Computer filed an 8-K (items 2.02 and 9.01): Results of Operations and Financial Condition; Financial Statements and Exhibits
Moved 9.5%, 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 7.5%, 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 5.3%, 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 4.7%, 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 4.0%, 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. None of them holds a row for this company inside that window.
Moved 3.6%, at or above the 3% floor for this strip
Headline describes Tesla demonstrating a levitating Roadster, a notable product event around the move.
News event dated 2026-10-16, MarketWatch Top Stories: Tesla demonstrates levitating Roadster 'flying car'
Moved 3.4%, 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 headline index rose 0.58% while the equal weight fund rose 0.36%, a gap of 0.22 points, a narrower spread than the prior session's but still pointing toward larger names outperforming the broader fund.
Nasdaq Composite rose 1.05% and Dow rose 0.69% while Russell 2000 rose only 0.27%, a split suggesting growth oriented large names outperformed smaller names this session.
Sector returns ranged from Technology up 1.68% to Communication Services down 1.09%, a wide spread beneath a modest headline index gain, pointing to uneven participation across sectors.
Participation rose to 4 of 8 tracked indices above their 50-day average from 3 of 8 previously, reaching half the tracked set but still not a majority.
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.