As the first half of 2026 draws to a close, the US stock market is revealing an increasingly pronounced two-tier structure. On one hand, the S&P 500 continues to climb, fueled by robust corporate earnings growth. On the other, this growth is becoming ever more concentrated among a handful of AI-focused companies. By June 2026, consensus forecasts for S&P 500 earnings growth have been significantly revised upward. However, the degree of internal divergence—and the resulting concentration risk—has become a growing concern for investors.
Growth Engine: Upward Earnings Revisions and Internal Divergence in the S&P 500
Since the start of 2026, several major financial institutions have raised their full-year earnings growth forecasts for the S&P 500. In its mid-year outlook, Schwab increased its estimate for annual earnings growth to 25%. Meanwhile, Goldman Sachs raised its year-end S&P 500 target to 8,000 points, citing the trajectory of corporate earnings as the key driver and projecting 2026 earnings per share to reach around $309. JPMorgan’s analysts further estimate S&P 500 earnings growth at about 22% for 2026 and suggest that, in an optimistic scenario, the index could hit 9,000 by mid-2027.
Yet, these headline numbers mask significant internal divergence. According to UBS, the technology-related sectors within the S&P 500 are expected to deliver earnings growth of around 20.5% in 2026, nearly matching the 21.7% increase projected for the "Big Six" tech giants. In contrast, non-tech sectors are forecast to grow earnings by only about 10%. In other words, tech sector growth is roughly double that of non-tech sectors. A closer look at the distribution of earnings revisions reveals that this upward momentum is also highly concentrated. Data from Evercore ISI shows that more than 40% of the S&P 500’s overall earnings upgrades for 2026 are attributable to just three companies: Micron Technology, Nvidia, and Alphabet. On the revenue side, S&P 500 companies are expected to see top-line growth of about 10%. However, profit growth is outpacing revenue gains, primarily because operating margins have reached historic highs—blended net profit margins hit 13.4% in Q1 2026, the highest in 15 years. The main drivers of margin expansion include productivity gains from AI and disciplined cost controls in a tight labor market. This means that about half of earnings growth is coming from margin improvement rather than revenue growth—a pattern that inherently carries greater sustainability risk.
From a sector perspective, Communication Services (led by Alphabet) and Information Technology (represented by semiconductor leaders like Micron, Intel, and Broadcom) are the primary engines of earnings growth. While overall earnings expectations for 2026 are broadening, as several investment banks have noted, the concentration of upward earnings revisions is unlikely to dissipate naturally in the short term. The ongoing expansion of AI-related capital expenditures remains the core catalyst for this cycle, and the return profiles and marginal benefits of these investments will largely determine the sustainability of earnings growth in the second half of the year.
Concentration Risk: The S&P 500 from Index to "Individual Stocks"
The sharp divergence in earnings growth is not only evident in company income statements but is also reflected more directly in index weightings. As of June 2026, the combined weight of the top 10 constituents in the S&P 500 is approaching 40%, setting a new record. Torsten Slok, Chief Economist at Apollo Global Management, has stated that the S&P 500 is "no longer a diversified index." This is not an exaggeration—the profit share of the top 10 companies has nearly doubled since 1996, with the US equity market increasingly dominated by a shrinking group of mega-cap firms.
Several factors are driving this concentration: rapid profit and revenue growth among a few tech and semiconductor companies; continued capital inflows—especially from passive ETFs—into large-cap stocks; and investors’ long-term expectations for AI-driven themes and high-margin businesses pushing valuations higher. As of June 2026, the top 10 companies by index weight are: Nvidia (8.24%), Apple (6.78%), Microsoft (4.86%), Amazon (4.20%), Alphabet Class A (3.68%), Broadcom (3.21%), Alphabet Class C (2.93%), Meta (2.10%), Tesla (1.90%), and Berkshire Hathaway (1.38%). Notably, Nvidia alone accounts for about 8% of the S&P 500, so any price movement in its shares has an outsized impact on the index.
This reallocation of sector weights reinforces the trend. Information Technology, Communication Services, and Consumer Discretionary—the first two being closely tied to AI themes—now collectively represent about 60% of the S&P 500, up from just 39% before ChatGPT’s debut. The S&P 500 is evolving from a broad barometer of the US economy into a theme-driven index centered on a handful of tech giants.
Such concentration brings structural risks. When the market corrects, higher concentration amplifies systemic risk: negative news or valuation adjustments among a few companies can trigger sharp index-level volatility, undermining the S&P 500’s effectiveness as a proxy for the broader economy. The market turbulence seen in Q4 2025 and Q1 2026, driven by swings in mega-cap stocks, serves as a recent warning.
Valuation Fragility: Ultra-Low Equity Risk Premium
Alongside concentration risk, valuation fragility is also emerging. The Equity Risk Premium (ERP)—the excess return investors expect from equities over risk-free assets like US Treasuries—is a critical gauge of market valuation safety. According to the Federal Reserve’s Financial Stability Report from May 2026, the current ERP has dropped to 2.7%, well below the 4.6% historical median since 1991 and near a two-decade low.
Specifically, the S&P 500’s forward earnings yield is about 4.7%, while the yield on 10-year Treasury Inflation-Protected Securities (TIPS) is close to 2.0%. The 2.7% spread represents the extra compensation investors receive for taking on equity market risk. Historically, this level is near the critical threshold seen before the ERP briefly turned negative during the dot-com bubble in 2000.
Market participants interpret this signal differently. Optimists argue that AI-driven investment is fueling rapid earnings growth, making stocks more attractive and justifying a lower ERP—essentially, the market is pricing in a "new productivity cycle." However, skeptics point out that a 2.7% risk premium means equities now offer only a slim valuation advantage over safe bonds. Should AI-driven earnings growth fall short—whether due to declining returns on capital expenditures or shifts in the macro environment—an overvalued market could face significant downside. If high earnings growth among AI-related companies slows, the current premium could compress sharply, leading to a pronounced valuation reset.
From an asset allocation perspective, a low ERP may also trigger a rotation from equities to bonds. When the returns on safe assets approach risk-adjusted equity yields, conservative investors may become increasingly motivated to rebalance toward fixed income.
Key Variables for the Medium-Term Outlook
In summary, the trajectory of the US equity market in the second half of 2026 will hinge on the interplay of three key variables.
The breadth of earnings growth is the first variable. Whether non-tech sectors can accelerate earnings growth in late 2026 or 2027 will directly affect market resilience. UBS expects that productivity gains from AI applications could broaden earnings growth in late 2026 and into 2027. If this fails to materialize, market vulnerability will remain concentrated in a few companies.
The efficiency of AI capital expenditures is the second variable. In 2026, hyperscale cloud providers are expected to spend over $500 billion on AI-related capex. The marginal returns on these investments will determine the sustainability of future earnings growth and are central to current market valuations. If returns fall short of expectations, overall earnings growth will come under pressure.
Macro uncertainty is the third variable. Factors such as tariff policy, a softening labor market, and sticky inflation continue to impact corporate costs and consumer spending patterns. Schwab’s analysts note that political volatility is "one of the most underpriced risks" in today’s market. Shifts in these external factors could unexpectedly trigger changes in market sentiment.
Gate US Stock Trading: Multi-Asset Allocation Amid Structural Divergence
For investors looking to participate in the US equity market under current conditions, flexible multi-asset allocation tools are more important than ever. With structural divergence between technology themes and traditional sectors, diversifying market risk and broadening allocation strategies have become key considerations.
On June 1, 2026, Gate officially launched live US stock trading services. Unlike the tokenized stocks or CFD (Contract for Difference) products commonly found on traditional crypto platforms, Gate’s new offering connects directly with Alpaca, a compliant broker-dealer with US brokerage and clearing licenses. This allows users to buy actual US stocks and ETFs directly on the platform.
In terms of coverage, Gate’s US stock trading supports over 10,000 stocks and ETFs listed on major US exchanges—including the New York Stock Exchange (NYSE) and Nasdaq. Users can buy and sell using USDT without currency conversion, with a minimum trade size of just 0.01 shares (starting from about $1).
A key feature is the cost structure for holding positions. Unlike stock CFDs on the platform, spot US stock trades do not incur any funding rates, swap fees, or overnight holding charges. This is a significant cost advantage for long-term, allocation-focused investors who want to enjoy shareholder rights. Additionally, if a held company pays a dividend, the payout is automatically credited to the user’s account in USDT.
For those seeking to participate in the structural AI rally of 2026, Gate’s US equity products offer direct access to AI-themed stocks. From semiconductor leaders like Nvidia and Micron to cloud giants like Alphabet and Microsoft, users can combine crypto assets and US equities within a single, familiar platform—eliminating the need to juggle multiple accounts and funding systems.
Gate’s live US stock trading is now available to eligible users. Access the stock section via the TradFi tab on the Gate website or app, transfer USDT to your stock account, and start trading. For detailed trading rules and a list of available securities, visit the relevant Gate platform pages.
Conclusion
The defining feature of the US equity market in the first half of 2026 can be summed up as follows: beneath robust macro-level growth lies a highly fragmented microstructure. The S&P 500 is advancing on optimistic 25% earnings growth forecasts, but its pillars of growth are concentrated in Communication Services and Information Technology, with the top 10 constituents accounting for nearly 40% of the index. Meanwhile, the equity risk premium has narrowed to an extreme, leaving the market highly dependent on "perfect" pricing—levels not seen in two decades. In this structural environment, regardless of your allocation strategy, understanding the nature of concentration risk and the deeper logic behind valuation fragility is essential for making rational investment decisions.
