LONDON, June 27 — The Trump bull market has been a magnificent beast, fed by AI hype, a record-breaking SpaceX IPO, and share buybacks that hit an all-time high in 2025. But quietly, while the champagne corks were still bouncing, the index committees changed the rules. And that technical detail under the hood could be the thing that brings the whole party to a juddering halt.
The numbers from the first Trump term are, on the face of it, extraordinary. The Dow rose 57%, the S&P 500 gained 70%, and the Nasdaq Composite surged 142%.
The current rally has been fuelled by what the market calls “IPO euphoria,” and nobody has delivered euphoria quite like Elon Musk’s SpaceX. When the company went public on June 12, it raised $75 billion, nearly tripling the previous record-holder, Saudi Aramco’s December 2019 IPO. SpaceX briefly touched a valuation of almost $3 trillion before its post-IPO gains were pared back.
Hot on its heels, Anthropic and OpenAI both filed confidentially with the Securities and Exchange Commission — on June 1 and June 8, respectively. By June 18, secondary markets were pricing Anthropic at an estimated $965 billion and OpenAI at $909 billion.
The technical reality is that the hype is thick enough to cut with a knife. But here is the detail that matters. Before SpaceX’s debut, several committees amended the rules for index inclusion.
The presumption is that Nasdaq Global Indexes wanted to court the world’s largest IPO to list on its exchange. The consequence, however, is that newly implemented rules can very easily turn the tables. As ever, the mechanism is simple.
When a stock is forced into a major index faster than the market can absorb it, passive funds must buy at any price. If the initial euphoria fades and the stock corrects — as SpaceX’s post-IPO valuation already has, paring its gains — the forced buying creates a distorted floor.
When that floor gives way, the selling can be violent. The Trump bull market has been built on three legs: AI, buybacks, and IPO mania. The index rule changes, designed to be accommodating, may have just sawed one of them off at the knee.
Watch the secondary-market valuations for Anthropic and OpenAI closely. If they start to wobble before the official listings, the fast-entry rules that were meant to be a welcome mat could become a trapdoor.
