The IPO Wave That Could Tip Concentration Past Every Bubble

Tiger’s desk passes along the latest from Bank of America strategist Michael Hartnett, and one figure carries the note: if SpaceX, OpenAI and Anthropic come public in quick succession, the combined weight of the leading AI names in the major US indices could climb to roughly 48% — a concentration beyond the Nifty Fifty, beyond Japan’s late-1980s peak, beyond the dot-com top. The three are pencilled into a tight window (SpaceX first, around mid-June; OpenAI targeting September; Anthropic perhaps October) at something like $4tn of combined private value.

The argument is not really about valuation multiples. It is mechanical. Once these names join the benchmarks, passive funds have to buy them in size, and active managers and retail have to sell something else to make room — and in a market already this top-heavy, that reshuffle can whip the existing momentum names around. The calendar makes it worse: the mid-June buyback blackout, quarter-end rebalancing and volatility-targeting flows all land in the same few weeks.

The core idea The worry is not the AI thesis — it is plumbing. Asking the market to absorb several trillion-dollar listings in a few weeks, into indices already this concentrated, is the kind of supply shock that can produce a sharp, sentiment-driven drop even if the underlying fundamentals hold up.

Where it fits

This is the same fragility our market-structure work reads from the other side. A tape carried by a handful of names is exposed to anything that moves the marginal dollar, and a forced index reshuffle is exactly that. It sits naturally next to the breadth read — and, as it happens, it is the same equity-supply risk that OnlyFin’s Wilfred Lim flags this month from a very different desk. Featured for the framing, not as our own forecast.