What history tells us about Marvell's upcoming S&P 500 inclusion

June 8, 2026 - 22:27

Marvell Technology shares have been climbing sharply after the announcement that the company will join the S&P 500 index on June 22. Investors are betting that the move will bring fresh demand from funds that track the benchmark. But history offers a mixed picture of what happens next.

Yahoo Finance Markets and Data Editor Jared Blikre examined how stocks have typically behaved in the days just before and after being added to the index. The pattern is not always a straight line up. In many cases, stocks see a pop on the news, then give back some of those gains once the actual addition happens. The reason is simple: index funds and institutional managers must buy shares ahead of the effective date, but that forced buying can create a temporary spike. Once the buying is done, the stock often drifts lower.

That said, the long-term track record for S&P 500 additions is generally positive. Companies that join the index tend to benefit from increased visibility, more analyst coverage, and a broader shareholder base. For Marvell, the chipmaker has already been riding a wave of enthusiasm around artificial intelligence and data center demand. The index inclusion adds another layer of momentum, but traders should be aware that the first few days after the switch can be volatile.