S&P 500: The Winners and Losers of August 2026
S&P 500: The Winners and Losers of August 2026
The S&P 500 gained roughly 2.5% in August 2026, a steady month at the index level that gave almost no indication of what was happening underneath. The split among constituents was close to even, with 255 stocks finishing the month higher and 245 finishing lower, yet individual moves ranged from a stock that more than doubled on a single clinical trial result to three names that lost roughly a quarter of their value apiece. What unites August’s extremes is that almost none of them were driven by the market. They were driven by company-specific news: a drug trial readout, a set of earnings reports, and a piece of state legislation. In this article, we break down the top winners and losers in the S&P 500 for August 2026 and examine the key drivers behind their stock movements.
Top S&P 500 Performers in August
Among the top performers were Moderna (MRNA), Palantir Technologies (PLTR), and Veeva Systems (VEEV). All three delivered genuinely new information to the market, though of very different kinds. Here’s a closer look at why each of these stocks stood out:
Moderna ($MRNA) +156%
Moderna, a biotechnology company built around messenger RNA technology and best known for its respiratory vaccine franchise, more than doubled in August after producing the first positive late-stage result for a personalized mRNA cancer therapy.
On August 19, Moderna and Merck announced interim Phase 3 results for intismeran autogene, Moderna’s individualized neoantigen therapy, combined with Keytruda in patients with resected high-risk melanoma. The trial met its primary recurrence-free survival endpoint and its key distant metastasis-free survival endpoint, with the companies describing the improvements as statistically significant and clinically meaningful and reporting no new safety signal. The stock rose as much as 160% that day, adding close to $40 billion in market value at one point.
The significance was not immediate revenue. The announcement created no 2026 product sales and Moderna did not raise financial guidance. What changed was probability. Moderna had been heavily dependent on respiratory vaccines, and a successful Phase 3 oncology readout materially increased the chance that its mRNA platform could produce a major commercial product outside that franchise. Detailed efficacy figures had not yet been presented and overall survival data were not yet mature, which leaves real uncertainty in place, but the result opened a plausible regulatory filing path and strengthened the read-through to Moderna’s other intismeran studies.
Late in the month, on August 28, Moderna priced an upsized $2.6 billion offering of 0.00% convertible senior notes due 2032, saying proceeds could support general corporate purposes including oncology growth and debt repayment. The offering was paired with a hedge intended to offset dilution. It acted as a modest counterweight to the rally rather than a driver of it, and it gave the company substantial capital to fund the opportunity the August 19 data had just created.
Palantir Technologies ($PLTR) +51%
Palantir Technologies, a software company that builds data analytics and AI platforms for government agencies and large commercial enterprises, rose roughly 51% in August after a quarterly report that beat expectations by an unusually wide margin and came with a large increase to full-year guidance.
On August 3, after the market close, Palantir reported second-quarter total revenue growth of 93% year over year, with U.S. commercial revenue growing 149%. U.S. government revenue rose 90% to $809 million, which mattered because it showed the strength was not confined to a single customer type.
The guidance raise was the part that justified a repricing. In its SEC-filed earnings exhibit, Palantir lifted full-year revenue guidance to a range of $8.150 billion to $8.158 billion, raised U.S. commercial revenue guidance to more than $3.424 billion from a prior $3.224 billion, implying at least 134% growth, and raised adjusted operating income guidance to $4.889 billion to $4.897 billion. Third-quarter revenue was guided to $2.160 billion to $2.164 billion.
Unlike Moderna, where value shifted because a clinical probability changed, Palantir’s catalyst ran straight through the income statement. The report raised the expected revenue base, the expected duration of growth, and the profit pool that valuation models draw on, all at once. The shares gapped higher after the release and then continued climbing through the rest of the month rather than giving back the initial move, which is consistent with investors progressively capitalizing the higher outlook rather than trading a single headline.
Veeva Systems ($VEEV) +40.20%
Veeva Systems, a cloud software company that builds industry-specific applications for pharmaceutical and biotechnology companies covering everything from clinical trials to sales operations, rose roughly 40% in August on a combination of two major customer wins and a quarter that beat expectations and lifted full-year guidance.
The stock was already climbing before the news arrived. By mid-August, Veeva had risen for ten consecutive sessions, a run worth roughly 25% that added about $8.3 billion in market value, well ahead of the broader market over the same stretch. That advance reflected a shifting view of enterprise software generally, as investors moved away from the assumption that AI would render application vendors obsolete.
On August 25, Veeva announced that both Biogen and Regeneron Pharmaceuticals had committed to Vault CRM globally, two marquee names migrating to the company’s newer platform on the same day. Vault CRM is the successor to Veeva’s legacy CRM product, and converting large customers onto it has been the central strategic question facing the company.
The quarter arrived the following afternoon. On August 26, after the close, Veeva reported fiscal second-quarter total revenue of $928.0 million, up 18% year over year and ahead of the roughly $905 million consensus, with subscription revenue of $766.8 million, up 16%. Non-GAAP earnings per share came in at $2.35 against expectations near $2.22, and non-GAAP operating income of $415.9 million lifted operating margin to 44.8%. CEO Peter Gassner said AI was opening the next chapter for Veeva and life sciences, and that Vault CRM had recorded its best quarter ever while the company’s Falcon product accelerated rapidly. More than 180 customers were live on Vault CRM by quarter-end, including five of the top 20 biopharma companies.
Management raised full-year fiscal 2027 revenue guidance to a midpoint near $3.685 billion from $3.64 billion, and lifted its non-GAAP earnings per share outlook to approximately $9.21. Third-quarter guidance also came in above expectations. Shares rose 15.2% the next day, at one point trading as much as 20.9% higher, closing at $286.48 against $244.91 the session before.
The reason the move was as large as it was has to do with what the quarter disproved. Software companies serving specialized industries had been discounted on the theory that AI would compress demand for their products. Veeva reported accelerating growth, expanding margins, and two of the largest biotech customers in the world committing to its newest platform, all in the same week.
Worst S&P 500 Performers in August
Among the biggest decliners in the S&P 500 for August 2026 were DaVita (DVA), Edison International (EIX), and The Trade Desk (TTD). The three declined for meaningfully different reasons: one company reset expectations without missing estimates, one was repriced by a legislature, and one delivered a genuine deterioration in its operating trajectory. Here’s a closer look at what drove their underperformance.
DaVita ($DVA) -26.69%
DaVita, a healthcare company that operates dialysis centers and treats patients with chronic kidney failure, fell roughly 27% in August, making it the index’s worst performer for the month despite a quarter that beat on earnings and left annual guidance intact.
On August 4, DaVita reported second-quarter revenue of $3.554 billion, operating income of $579 million, and diluted earnings per share of $4.02, above the roughly $3.88 consensus. Cash from operations was $490 million. On the headline numbers, this was not a disappointing quarter.
The problem was in the operating detail. Normalized non-acquired U.S. dialysis treatment growth was just 0.3% year over year, and revenue per treatment slipped sequentially to $415.87 from $417.59. In its SEC-filed earnings exhibit, management maintained rather than raised full-year guidance, holding adjusted earnings per share at $14.10 to $15.20 and adjusted operating income at $2.15 billion to $2.25 billion. The company also identified an Affordable Care Act enrollment headwind worth roughly $40 million in 2026 and $70 million in 2027. Shares fell as much as 7% in after-hours trading.
Sentiment pressure compounded the reset. Berkshire Hathaway sold 182,980 DaVita shares in a transaction dated July 31, disclosed around the earnings window, and its mid-August 13F made a broader quarter-end reduction visible. The 13F is backward-looking, reporting holdings as of June 30, so it is better understood as reinforcement than as evidence of August selling.
The important point is the counterfactual. DaVita did not miss earnings and did not cut guidance, so a 27% monthly decline cannot be described as the mechanical result of a shortfall. The stock had entered August after a strong run and was priced for exceptional execution. When the quarter delivered only respectable execution, the multiple compressed. The decline was gradual rather than a single gap, with the stock deteriorating steadily from around $240 at the end of July to roughly $176 by month-end.
Edison International ($EIX) -26.43%
Edison International, the parent company of Southern California Edison, fell roughly 26% in August, with almost the entire loss occurring in a single session on the final trading day after state legislation failed to deliver the wildfire liability protections investors had expected.
Edison entered the month carrying substantial event risk from the January 2025 Eaton Fire. Its second-quarter 10-Qdisclosed that SCE considered it likely its equipment was associated with the fire’s ignition, that it had recorded $1.6 billion of Eaton-related settlement losses, and that it was currently unable to reasonably estimate the range of losses it could ultimately incur. The filing also disclosed expected recoveries of $917 million from customer-funded self-insurance, $645 million from the Wildfire Fund, and $70 million through FERC rates. On August 4, a Los Angeles County investigation concluded that sparks associated with an out-of-service SCE transmission tower caused the fire. On August 11, a judge tentatively rejected an argument that SCE should be automatically liable under inverse condemnation principles, a partial offset that did not remove the broader exposure.
The decisive event came at month-end. California’s substantially revised Senate Bill 492 was published on August 29 and amended in the Assembly the same day. The text created a wildfire fast-pay program and other reforms, but did not deliver the broad shift of insurer and subrogation liability away from utilities that earlier proposals had led investors to anticipate. On August 30, SCE issued an unusually direct statement saying the amended bill did not deliver the reform California needed and did not address the stable financing framework utilities require to access capital at reasonable cost.
On August 31, Edison fell about 23% in one session, dropping from roughly $70 on August 28 to around $54. Nothing about the company’s current cash flows changed that day. What changed was the distribution of potential future wildfire losses and the cost of financing against them. A legislative framework that did less than expected to cap, shift, or fund those exposures warranted a higher equity risk premium even without a new accounting charge.
The Trade Desk ($TTD) -23.95%
The Trade Desk, a demand-side advertising platform that lets marketers buy digital ad inventory programmatically, fell roughly 24% in August after a quarterly report that showed sharp growth deceleration and guided the following quarter well below what analysts had modeled.
On August 6, The Trade Desk reported second-quarter revenue of $715 million, an increase of just 3% year over year and roughly 5% below the pre-report consensus of about $753 million. Net income fell to $64 million from $90 million. Adjusted EBITDA declined to $241 million from $271 million, with margin compressing to 34% from 39%. A 3% revenue increase paired with lower EBITDA dollars means the incremental economics of the business deteriorated during the quarter.
The forward guidance did more damage than the quarter itself. In its SEC-filed earnings exhibit, the company guided third-quarter revenue to at least $650 million and adjusted EBITDA to approximately $160 million. That revenue floor sat nearly 20% below Street models. The stock hit a new 52-week low as investors reset growth expectations, and analyst downgrades and target cuts followed over the next several sessions.
This was the most concrete fundamental reset of the three decliners. A growth company can absorb a modest earnings miss if the forward trajectory holds. Here the company showed decelerating revenue, lower profit dollars, a compressed margin, and a weak outlook simultaneously. The shares gapped down after the report and then traded at a persistently lower level for the rest of the month rather than recovering, which is what a durable forecast revision looks like as opposed to a temporary sector shock.
What the Month Really Said
August’s extremes divide cleanly into two categories, and the distinction is worth holding onto. Moderna, Palantir, Veeva, and The Trade Desk all received genuinely new operating or clinical information. A trial succeeded, two businesses accelerated beyond expectations, and one decelerated sharply. Those are moves you can trace directly to a disclosure that changed what the company is worth.
Edison International and DaVita are different. Edison’s cash flows did not change on August 31. What changed was the range of outcomes investors had to price, once it became clear that the legislature would not absorb as much wildfire liability as expected. DaVita did not miss earnings or cut guidance at all. It simply reported a respectable quarter while priced for an exceptional one, and the gap between those two things cost it a quarter of its value.
For a month in which the index rose 2.5%, the lesson is that the aggregate told you almost nothing. The largest moves came from a melanoma trial, a California bill, and four earnings reports, none of which had anything to do with each other.
This article is for informational purposes only and is not investment advice or a solicitation to buy or sell securities. The content is based on publicly available information and reflects the author’s opinions as of the publication date, which may change without notice. All investments carry inherent risks, including the potential loss of principal, and past performance is not indicative of future results. Readers should conduct their own research or consult a financial advisor before making investment decisions. BBAE holds no position in the securities mentioned, nor are they compensated by the companies mentioned.
