June 22, 2026, marked Marvell Technology’s (MRVL) official inclusion in the S&P 500 Index. This semiconductor company, headquartered in Santa Clara, California, has risen from a mid-cap stock to a member of the most important benchmark index in the US, thanks to its deep expertise in AI data center infrastructure. This inclusion isn’t just a routine index adjustment—it triggers a massive forced buying mechanism by passive funds, creating structural impacts on MRVL’s short-term liquidity and pricing.
Forced Buying by Passive Funds: Scale and Mechanism
The S&P 500 is one of the world’s largest stock indices in terms of assets tracked. As of June 2026, the three largest ETFs tracking the index—Vanguard S&P 500 ETF (VOO), iShares Core S&P 500 ETF (IVV), and SPDR S&P 500 ETF Trust (SPY)—collectively managed over $2.6 trillion in assets. VOO alone surpassed $1 trillion in assets in June 2026, becoming the world’s first trillion-dollar ETF. Whenever these passive funds and numerous institutional portfolios use the S&P 500 as their performance benchmark, any change in index constituents triggers programmatic portfolio rebalancing.
For Marvell’s inclusion specifically, passive funds must complete their purchases before the effective date. According to index adjustment rules, the weighting of a new constituent is determined by its market capitalization relative to the total index market cap. On the eve of inclusion, MRVL’s market cap stood at approximately $271 billion. The total market cap of the S&P 500 hovered around $50 trillion, giving MRVL an initial weighting of about 0.5%. This means the three major ETFs alone would need to purchase roughly $13 billion worth of MRVL shares. Factoring in other index-tracking mutual funds, pension funds, and insurance capital, total passive buying could reach several tens of billions of dollars. This "forced buying by passive funds" is the core mechanism supporting the stock price around the inclusion date—buyers aren’t acting on MRVL’s fundamentals, but because they are "required to hold" it.
The Historical Pattern of "Inclusion Day Premium"
The inclusion day premium is not a new concept. Both academia and Wall Street have studied it for decades.
According to a study by S&P Global, stocks added to the S&P 500 between 1995 and 1999 outperformed the index by 8.3 percentage points from announcement date to effective date; from 2000 to 2010, this excess return fell to 3.6 percentage points. Another study analyzing data from 1989 to 2006 found significant, statistically valid abnormal positive returns on the announcement day, with this effect persisting until the actual inclusion date.
However, post-inclusion performance tells a different story. Research from McKinsey shows that stocks added to the S&P 500 tend to revert to their pre-inclusion price levels within about 35 trading days. Strategas Securities analyzed 160 stocks added to the S&P 500 between 2015 and 2024, finding that these stocks outperformed the index by an average of 4800 basis points before inclusion, but underperformed by 66 basis points on average in the 12 months after. More broadly, statistics covering 1,926 constituent changes since 1957 indicate that new constituents generally outperform the market before inclusion, but often lag behind the S&P 500 after officially joining. Data since 2010 shows that new constituents lag the broader market by a median of about 1% in the quarter after inclusion, and about 2% after six months.
The logic behind this pattern is straightforward. Pre-inclusion excess returns mainly stem from two sources: anticipatory buying related to the event, and improvements in company fundamentals—being added to the S&P 500 signals that a company has reached certain thresholds in market cap and profitability. Relative weakness after inclusion is partly due to "buy the rumor, sell the news" trading behavior, as well as the fading of short-term buying momentum once passive funds have completed their purchases.
For MRVL, its pre-inclusion rally has been substantial—by June 18, 2026, the stock closed at $310.58, up 265.47% year-to-date and 314.38% over the past 52 weeks. This suggests that much of the inclusion premium may have already been priced in ahead of the effective date.
How Marvell Got Here: From Connectivity Chips to Trillion-Dollar Narratives
Marvell’s entry into the S&P 500 is fundamentally driven by explosive growth in its AI data center business.
In the first quarter of fiscal 2027 (ending May 2, 2026), Marvell posted net revenue of $2.418 billion, up 28% year-over-year and 9% quarter-over-quarter, marking a new single-quarter record. Data center business contributed $1.833 billion, up 27% year-over-year and 11% quarter-over-quarter, accounting for 76% of total revenue. The company has raised its full-year fiscal 2027 revenue guidance to about $11.5 billion, representing roughly 40% growth, and set its fiscal 2028 revenue target at around $16.5 billion.
Marvell’s business now rests on three pillars: custom AI chips (ASIC/XPU), data center interconnects, and optical networking. In custom ASICs, Marvell and Broadcom together form a de facto duopoly, controlling about 95% of the market. In March 2026, NVIDIA announced a $2 billion strategic investment in Marvell, with deep technical collaboration focused on NVLink Fusion. NVIDIA CEO Jensen Huang publicly called Marvell "the next trillion-dollar company" during his Computex keynote in June 2026. That day, MRVL shares surged 32.52% to $290.79, with market cap jumping by about $62.4 billion in a single day.
Yet the trillion-dollar narrative must withstand scrutiny. Before Huang’s remarks, MRVL’s market cap was around $192 billion; after the surge, it broke through $250 billion. On the eve of inclusion, market cap was about $271 billion. To reach $1 trillion, Marvell needs to triple its market value. This requires sustained, extraordinary revenue growth over the coming years—management has set a target for custom chip business revenue to exceed $10 billion annually by fiscal 2029, but even then, further valuation expansion will depend on continued performance.
Optical Interconnect: The Undervalued Growth Engine
Market perception of Marvell often centers on custom ASICs, but optical interconnect may be its more durable growth driver.
Management noted that interconnect business grew over 70% in 2026, with scale-out business growing even faster. Core products include PAM4 DSPs, TIAs, and drivers. The shift from copper to optical ("optics in, copper out") is becoming reality. One of the main focuses of NVIDIA’s $2 billion investment is Marvell’s optical networking chips for AI data center infrastructure. Marvell will begin sampling the world’s first 1.6Tbps 2nm coherent optical solution in the second half of 2026, targeting long-haul transmission between data centers spanning hundreds to thousands of kilometers.
Unlike custom ASICs, which face competition from in-house development (such as ByteDance accelerating its own AI chip development, causing MRVL shares to plunge nearly 10% on June 9, 2026), optical interconnect benefits from a structural trend: AI computing is shifting from centralized to distributed architectures. Large language model tasks are split across thousands of nodes for parallel processing, making connectivity an indispensable foundation. Regardless of which company supplies the compute chips, the need for high-speed data transmission between chips is non-negotiable. This structural feature may give optical interconnect a deeper moat than custom chips.
Conclusion
Marvell’s inclusion in the S&P 500 is the most iconic event in the 2026 US equity index rebalancing. The forced buying by passive funds will provide short-term support for MRVL around the effective date, but historical data shows that inclusion premiums are often "priced in early and revert after the event." For investors, understanding this mechanism and historical pattern is more important than simply chasing the inclusion event itself.
Marvell’s fundamental story—its duopoly position in custom ASICs, the enduring growth logic of optical interconnect, strategic partnership with NVIDIA, and $2 billion capital infusion—forms the basis of its long-term value. However, the path to a trillion-dollar market cap will require sustained delivery on performance.
