The Rational Reminder Podcast

Episode 406: When Massive Private Companies Go Public

30 snips
Apr 23, 2026
They unpack how mega IPOs like SpaceX or OpenAI could force index funds to buy newly listed shares and why that matters. They discuss why newly public stocks often underperform and how index rules and free float shape inclusion and weights. They explore research on fast-track inclusion, low-float risks, and alternative indexing approaches. The conversation focuses on market structure, rebalancing effects, and practical trade-offs for investors.
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INSIGHT

Free Float Dramatically Cuts Indexed Weight

  • Free float determines index weight, so a huge headline market cap can translate to a much smaller index weight if public float is low.
  • Felix uses SpaceX as example: a $1.75T valuation with 5% float equals an $88B indexed weight.
INSIGHT

Index Rules Vary So Mega IPO Impact Differs

  • Index inclusion and weighting rules vary across providers, so some indices may exclude low-float IPOs even if headline market caps are huge.
  • Felix points out CRSP/VTI keep a 10% float cutoff for fast-track entry, making VTI unaffected currently.
INSIGHT

IPOs Tend To Underperform Established Firms

  • IPOs historically underperform seasoned firms on secondary markets; termed the "new issues puzzle."
  • Jay Ritter's study found new issues returned ~5% vs 12% for similar listed firms from 1970–1990, a large long-term gap.
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