SpaceX entry drives index reshuffle as market concentration rises
What’s moving within the indexes
The September ranking brought notable reclassifications across size and style segments. In the large-cap space, Seagate Technology Holdings and Western Digital Corp moved fully into mega-cap, reflecting durable gains tied to artificial intelligence demand.
Moderna, meanwhile, initiated a packet from small-cap to mid-cap after surging more than 200% between the June and September ranking dates – though the company must hold its relative position through the next ranking before completing that transition.
On the style side, more than 100 securities changed their growth or value classification during the September ranking. Intel packeted toward growth across multiple indexes following improvements in growth expectations, while McDonald’s, Uber Technologies, Adobe, and Intuit moved toward value. Dell Technologies packeted toward growth in the large- and core-cap indexes (but not mega-cap) reflecting that its growth profile was less distinctive relative to mega-cap peers than within the broader large-cap universe.
Honeywell International’s index treatment illustrated the complexity that corporate actions introduce at reconstitution. Following Quantinuum’s public listing on June 4, 2026 – a spinout of Honeywell Quantum Solutions and Cambridge Quantum – and the June 29 spinoff of Honeywell Aerospace, both new entities were added to the Morningstar indexes to ensure the original investment in Honeywell International was fully captured in index returns.
What comes next
Looking ahead, Morningstar’s report flags additional mega-cap IPOs on the horizon – specifically Anthropic and OpenAI – as potential drivers of continued upward pressure on top-level concentration. If those listings proceed, the mega-cap segment will likely require further adjustment to keep the Morningstar Market Indexes aligned with the evolving market structure.
