Why It Moved · Market · 2026-10-20

Why it moved, October 20: Supermicro +13%, Equifax +11%, Hasbro +11%

On Tuesday, October 20 the S&P 500 rose 0.3% and 403 of 500 member stocks finished higher. These were the five biggest moves among S&P 500 stocks, and what was behind each.

The biggest S&P 500 moves, October 20

Company	Move	vs usual day	Year to date	Where it stands
Supermicro (SMCI)	+12.6%	3.2x	+23.5%	-34% from high · above 200-day
Equifax (EFX)	+11.3%	6.4x	-17.9%	-24% from high · below 200-day
Hasbro (HAS)	+11.2%	8.4x	+36.6%	at a 52-week high · above 200-day
Intuitive Surgical (ISRG)	-9.9%	6.4x	-31.1%	-34% from high · below 200-day
General Motors (GM)	-6.8%	4.3x	-4.6%	-14% from high · below 200-day

"vs usual day" compares the move with the stock's average daily move (up or down) over the past year. "Where it stands" is the distance from the 52-week high and the position against the 200-day average. Stocks with a one-day change over 60% (usually a spin-off or split) are left out.

What this means

Supermicro (SMCI) rose 12.6%. That is about 3 times its usual daily move. No company news, filing or industry move explains it; moves like this often reflect large investors adjusting positions.
Equifax (EFX) rose 11.3% as MarketWatch reported “Equifax Shares Rise as AI Cost Savings Offset Mortgage Headwinds”¹. That is about 6 times its usual daily move. It reported quarterly results.
Hasbro (HAS) rose 11.2% after the company raised its outlook² and results came in ahead of expectations³. That is about 8 times its usual daily move.
Intuitive Surgical (ISRG) fell 9.9%. That is about 6 times its usual daily move. It reported quarterly results; options had priced a move of about ±13%.
General Motors (GM) fell 6.8% as WSJ reported “General Motors Stock Slides as Iran Conflict Drives Up Costs”⁴. That is about 4 times its usual daily move. It reported quarterly results; options had priced a move of about ±3%.
A big one-day move tells you what the market learned that day, not where the stock goes next: large moves partly reverse about as often as they continue.

Sources

MarketWatch, Oct 20, 2026: Equifax Shares Rise as AI Cost Savings Offset Mortgage Headwinds
WSJ, Oct 20, 2026: Hasbro Lifts Outlook on Surging Magic Card Game Sales
Barron's, Oct 20, 2026: Hasbro Stock Rises as Earnings Beat Estimates on Magic Trading Card Growth
WSJ, Oct 20, 2026: General Motors Stock Slides as Iran Conflict Drives Up Costs

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Prices from Torvanta's end-of-day data; filings from SEC EDGAR. News context is drawn from the coverage cited below and may not be the whole cause of a move. Research only, not investment advice or a recommendation to buy or sell any security. Rankings change as data changes and can be wrong. Torvanta and its founder may hold positions in securities discussed. Past performance does not guarantee future results.

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