AI Stocks Gain Traction as 4 Companies Join S&P 500 Index

The S&P 500 has added 4 AI-related stocks to its index, signaling broader industry growth. Amidst this trend, buying opportunities may be emerging in beaten-down AI stocks. One such article recommends investing in specific AI companies before the next bull market.

Four AI infrastructure companies officially joined the S&P 500 on March 23, 2026, following S&P Global's announcement on March 6: Vertiv Holdings (VRT), Lumentum Holdings (LITE), Coherent (COHR), and EchoStar (SATS). The additions replaced Match Group, Molina Healthcare, Lamb Weston, and Paycom Software, reflecting a structural rotation out of consumer-facing and healthcare names into AI infrastructure plays. On announcement day alone, Lumentum surged 8%, EchoStar jumped 6.7%, and Coherent gained 4%, while Vertiv added 0.7%.

Three of the four additions are direct picks-and-shovels beneficiaries of the AI data center buildout. Lumentum and Coherent produce optical networking components that move data at the speeds AI training clusters demand — Nvidia had already committed $2 billion in investments across both companies for optical networking R&D before the index additions. Vertiv designs power and cooling systems for hyperscale facilities, a market where capacity constraints have become a bottleneck for AI deployment. EchoStar, though more of a satellite communications play, rounds out the quartet with exposure to connectivity infrastructure. S&P 500 inclusion triggers mandatory purchases by index funds and ETFs that collectively hold trillions in passive assets, providing a structural demand floor beneath these stocks.

The additions underscore a broader trend: AI representation in major indices is expanding beyond the hyperscalers into the enabling layer. Nvidia already represents roughly 8% of the S&P 500 alone, and Broadcom contributes 3.85%, meaning the top AI-adjacent names now command outsized index weight. With passive fund inflows tied to the index rising each quarter, newly added AI infrastructure stocks receive a recurring institutional bid that can compress volatility and support valuation multiples even during sector pullbacks. Investors tracking the AI infrastructure theme now have expanded S&P 500 exposure without requiring active stock selection.