Lumentum Joins the S&P 500 Soon: Buy the Dip Before the Index Funds Have To?

By Trey Thoelcke Published Mar 12, 7:35AM EDT

Quick Read

Lumentum’s S&P 500 inclusion on March 23, 2026, creates a date-certain forced-buying event as all passive index funds must purchase shares to match the company’s weighting, introducing near-term demand pressure regardless of the ongoing valuation debate.

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Lumentum Joins the S&P 500 Soon: Buy the Dip Before the Index Funds Have To? — © Bet_Noire / iStock via Getty Images

With Lumentum’s (NASDAQ: LITE | LITE Price Prediction) inclusion in S&P 500 effective March 23, 2026, passive index funds face a date-certain obligation to buy shares regardless of valuation. The question is how the mechanical buying pressure may affect price action around the inclusion date.

Lumentum currently trades around $672, well off its 52-week high of $783.80. The stock is up 82.32% year-to-date, while the S&P 500 is down 0.82% over the same period.

The Bull Case: Fundamentals Back the Hype

The operating momentum is hard to dismiss. In Q2 FY26, Lumentum posted $665.5 million in revenue, up 65.5% year-over-year, with non-GAAP operating margin expanding 1,730 basis points to 25.2%. Q3 guidance calls for $780 million to $830 million in revenue, implying over 85% YoY growth.

Two emerging product lines anchor the forward story. The optical circuit switch backlog exceeds $400 million, and co-packaged optics recently secured an incremental multi-hundred-million-dollar order deliverable in the first half of calendar 2027. CEO Michael Hurlston framed the scale of the opportunity directly: “Our results continue to highlight the strength of our roadmaps for both optical components and systems, which make us mission-critical to the world’s AI leaders.”

Nvidia has made a $2 billion strategic investment alongside a multibillion-dollar purchase commitment for laser components, and one valuation model pegs fair value at $853, implying roughly 21% upside from current levels. Analyst sentiment skews bullish: 18 Buy ratings versus four Holds, with zero Sell ratings. Citigroup carries an $800 price target, while the consensus analyst target sits at $660.32.

The Bear Case: Valuation and Insider Signals

The risks are real. At a trailing P/E of roughly 196x, even believers must acknowledge the execution premium baked in. Insiders have been selling aggressively: $38.85 million in insider sales followed the post-earnings run-up, including CEO Michael Hurlston selling 20,169 shares at $551.99 on February 7. Some institutional holders trimmed positions, with Schroder cutting its stake by 41.4% and Picton Mahoney by 47.8%. Lumentum also carries $3.24 billion in current long-term debt, a material balance sheet risk. CNBC’s Jim Cramer has said he would be a seller at current levels.

The Index Inclusion Tiebreaker

The valuation debate may be secondary to the mechanics of March 23. When a stock enters the S&P 500, every passive fund tracking the index must purchase shares in proportion to the company’s weighting. With Lumentum’s market cap near $48 billion, that represents a non-trivial forced-buying event on a fixed date. The fundamental debate does not go away, but the inclusion date introduces a near-term demand event driven by passive fund mechanics, independent of earnings or guidance.

About the Author Trey Thoelcke →

Trey has been an editor and author at 24/7 Wall St. for more than a decade, where he has published thousands of articles analyzing corporate earnings, dividend stocks, short interest, insider buying, private equity, and market trends. His comprehensive coverage spans the full spectrum of financial markets, from blue-chip stalwarts to emerging growth companies.

Beyond 24/7 Wall St., Trey has created and edited financial content for Benzinga and AOL's BloggingStocks, contributing additional hundreds of articles to the investment community. He previously oversaw the 24/7 Climate Insights site, managing editorial operations and content strategy, and currently oversees and creates content for My Investing News.

Trey's editorial expertise extends across multiple publishing environments. He served as production editor at Dearborn Financial Publishing and development editor at Kaplan, where he helped shape financial education materials. Earlier in his career, he worked as a writer-producer at SVE. His freelance editing portfolio includes work for prestigious clients such as Sage Publications, Rand McNally, the Institute for Supply Management, the American Library Association, Eggplant Literary Productions, and Spiegel.

Outside of financial journalism, Trey writes fiction and has been an active member of the writing community for years, overseeing a long-running critique group and moderating workshop sessions at regional conventions. He lives with his family in an old house in the Midwest.