Jeremy Grantham, co‑founder of Grantham, Mayo, & Co., warned investors to watch early warning signs that precede market collapses. He cited the meteoric rise of SpaceX valuations as a modern illustration of exuberance detached from fundamentals. Grantham argued that rapid price spikes, media frenzy, and speculative financing often signal an unsustainable bubble forming. Such patterns echo historic excesses and merit close scrutiny by portfolio managers.

Grantham contrasted the SpaceX surge with the infamous South Sea bubble of the 18th century, noting that both episodes featured over‑optimistic expectations and weak underlying earnings. He highlighted that modern markets, with algorithmic trading and low‑interest rates, can amplify distortions faster than in past centuries, raising the stakes for risk‑averse investors. They must therefore re‑evaluate exposure to high‑growth tech stocks.

For fund managers, Grantham’s framework translates into tighter valuation screens and heightened scrutiny of cash‑flow sustainability. Companies riding hype without solid profit trajectories may see sharp corrections, eroding portfolio returns. By applying these historical lessons, investors can avoid being caught in the next wave of overvaluation, preserving capital when sentiment turns. The approach offers a disciplined hedge against speculative excesses.