Key HighlightsMarket concentration has reached unprecedented levels, with the 10 largest stocks comprising nearly 40% of the S&P 500Three companies—Micron, Nvidia, and Alphabet—drove more than 40% of positive 2026 earnings estimate adjustmentsEvercore ISI projects the S&P 500 to reach 7,750 by year-end, with an optimistic scenario targeting 9,000AI-driven industries (technology, communication services, consumer discretionary) have expanded to approximately 60% of index compositionCore PCE inflation climbed to 3.3% on an annual basis, marking the steepest increase since 2023 and heightening economic concernsA handful of artificial intelligence powerhouses are increasingly responsible for the S&P 500’s overall trajectory, according to fresh analysis from Evercore ISI. The research firm cautions that this heightened concentration presents a double-edged sword for market participants.Unprecedented Market NarrownessAnalysts at Evercore, led by Julian Emanuel, characterize today’s S&P 500 as a “market of stocks” instead of a genuine stock market. This distinction highlights how a limited number of mega-cap names are shouldering the bulk of index gains while most constituents lag behind.The largest 10 holdings within the benchmark index have swelled to represent nearly 40% of its entire market capitalization. This marks an all-time peak. The year’s equity market advances are far from evenly distributed across the 500 companies.Micron, Nvidia, and Alphabet collectively accounted for over 40% of all upward adjustments to 2026 earnings projections for the S&P 500. These three technology leaders also delivered some of the most impressive earnings beats during the latest quarterly reporting cycle.Micron Technology, Inc., MUThe technology, communication services, and consumer discretionary sectors have ballooned to represent approximately 60% of the S&P 500’s total weight. When OpenAI released ChatGPT, these sectors combined for merely 39% of the index.Artificial Intelligence Obscures Underlying Economic WeaknessesWhile AI-driven equities propel the index to new heights, the fundamental economic landscape tells a more complicated story. Consumer confidence remains depressed, crude oil prices stay elevated, and inflationary pressures persist.The core Personal Consumption Expenditures (PCE) index advanced to 3.3% year-over-year, representing its most aggressive pace since 2023. Under normal circumstances, such macroeconomic conditions would severely hamper equity valuations.Yet artificial intelligence enthusiasm has counterbalanced these negative forces. According to Evercore’s research, first-quarter 2026 earnings surprises reached magnitudes typically associated only with post-recession recovery periods.The investment firm reaffirmed its S&P 500 year-end price objective of 7,750. Under a bullish scenario, Evercore envisions the benchmark climbing to 9,000, fueled by sustained AI infrastructure investment and robust profit expansion.Despite the extreme concentration, Evercore contends that technology sector multiples remain sensible from a historical perspective relative to the overall market. This makes the sustainability of earnings momentum the critical variable.Nevertheless, the firm acknowledged that concentrated leadership amplifies downside vulnerability. Should investor sentiment sour or geopolitical risks intensify, the index could retreat toward its 200-day moving average, currently positioned near 6,800.International Markets Mirror the Technology ShiftThe artificial intelligence narrative extends well beyond American borders. Technology’s representation within the MSCI Emerging Markets index has surged to 42%, now surpassing its proportion of the S&P 500.Taiwan and South Korea have experienced market capitalization expansion that now approaches India’s total valuation, driven predominantly by their integral roles in the global technology manufacturing ecosystem.Evercore’s market perspective hinges on a fundamental question: can artificial intelligence demand maintain sufficient momentum to sustain earnings acceleration? Through the first months of 2026, evidence suggests the answer remains affirmative.The post Three AI Giants Are Propping Up the Entire S&P 500 — Should Investors Worry? appeared first on Blockonomi.