Q3 Review: S&P 500 Risers & Fallers in Q3

Oil refiners, AI hardware makers and a biotech comeback led the S&P 500 over the past quarter, while utilities, housing-linked names and a handful of broken growth stories dragged at the bottom.

The index managed a modest gain of around 2% in Q3, but that headline figure hides one of the widest gaps between sectors in years. Energy rallied more than 16% while utilities fell more than 12%, and the biggest individual moves came from stocks with their own catalysts rather than the market tide.

Top S&P 500 Movers in Q3

Three-month performance as of 6 October, broadly covering the third quarter.

Risers

Fallers

Higher Yields and Oil Split the Market

The quarter's macro backdrop rewarded companies that profit from the energy shock and punished those that depend on cheap borrowing.

Middle East supply disruption kept oil and fuel prices elevated, lifting energy to the top of the sector table and pushing three refiners into the top ten. The same inflation pressure drove the Fed's first rate hike since 2023 and sent long-dated Treasury yields to their highest levels in nearly two decades.

That hit rate-sensitive sectors hardest, with utilities, real estate, industrials and consumer discretionary stocks all finishing the quarter in the red. Utilities fell furthest despite strong power demand from AI data centres, a sign of how heavily higher yields weighed on income-focused stocks that compete with bonds.

Refiners Cash In on the Diesel Squeeze

Marathon Petroleum, Valero and Phillips 66 all gained more than 50% as refining margins hit record levels.

The ultra-low sulphur diesel crack spread climbed above $100 a barrel during the quarter, surpassing anything seen during the 2022 energy crisis, as tight global distillate supplies met fresh disruption in the Middle East. US diesel prices set a new record in September, and the refiners strung together six straight weeks of gains into mid-September.

The windfall is already showing up in results, with Marathon's refining margin roughly doubling to $36.33 a barrel in the second quarter. That has funded heavy buybacks and dividends, adding to the appeal for investors.

AI Hardware Trade Broadens

Four of the top ten risers were hardware makers, as the AI spending boom spread beyond chips into servers, storage and PCs.

Hewlett Packard Enterprise and Super Micro Computer jumped in September after Oracle reaffirmed plans for $90bn to $95bn of capital spending this year, much of it on data centre equipment. Super Micro also pointed to a $60bn order backlog, underlining the scale of demand for AI servers.

NetApp's revenue rose around 30% in its latest quarter as all-flash storage sales climbed 47% on AI infrastructure deals, prompting a raised full-year outlook. HP Inc hit a 52-week high in September on hopes that AI-capable PCs will drive a new upgrade cycle.

Biotech Breakthrough and Software Relief

The quarter's biggest winner by far was Moderna, which more than doubled on a breakthrough in its cancer vaccine programme.

Moderna and Merck reported positive Phase 3 results in August for their mRNA-based therapy combined with Keytruda in high-risk melanoma, meeting the trial's primary goal of recurrence-free survival. Chief executive Stéphane Bancel called it "a pivotal moment for the field of cancer research," and FDA approval of updated Covid-19 vaccines added further support.

In software and services, Paycom surged after beating second-quarter forecasts and raising guidance, while Accenture's results on 1 October triggered its biggest one-day gain on record. Accenture's rally reflected relief that AI has not yet eroded demand for consulting, with the company signing a record 141 deals worth more than $100m each in its fiscal year.

Utilities and Housing Feel the Rate Squeeze

Three utilities and two housing-linked companies made the fallers list, all exposed in different ways to higher borrowing costs.

Edison International and PG&E suffered the sharpest falls at the end of August after California's wildfire bill advanced without a liability cap for utilities, with Edison posting its biggest one-day drop in more than 25 years. NRG Energy slid as rising Treasury yields weighed on the sector more broadly.

Builders FirstSource cut its 2026 outlook after second-quarter sales fell nearly 9% and single-family construction volumes dropped, as high mortgage rates kept a lid on housebuilding. Pentair fell 17% in a single session in July after slashing guidance on severe inventory destocking in its pool equipment business.

Broken Deals and Disrupted Franchises

The rest of the fallers were hit by company-specific setbacks that challenged what investors had been paying up for.

Fair Isaac, the worst performer, lost around a quarter of its value on 29 September after the FHFA said Fannie Mae and Freddie Mac would treat FICO and rival VantageScore equally on pricing. Rocket Mortgage also said it would switch to VantageScore as its preferred model, a direct challenge to FICO's dominance in mortgage lending.

MGM Resorts dropped 10% in a day in September after Barry Diller's People Inc. withdrew its $48.30-a-share buyout proposal. Axon slid after removing cash flow guidance and announcing a $1bn convertible bond, while Rollins fell after residential growth slowed to 3.6% in the second quarter.

What to Watch in Q4

Third-quarter earnings season kicks off this month and will test whether the leaders can justify their gains.

Refiners face the risk that margins ease if supply disruptions fade, while rate-sensitive sectors need a pause in the rise in yields to stage a recovery. Quarterly leaderboards also mix lasting trends with one-off jumps on news and deals, so the coming months will help separate the two.