Episode summary
He Invested Through Five Bubbles. He Wrote the Book on Them | What We Learned This Week
Excess Returns
· · Hosts: Matt Zeigler, Jack Forehand, Justin Carbonneau, Dave Nadig, Brent Kochuba, Kai Wu, Eric Pachman · Guests: Jeremy Grantham, Andy Constan, Edward Chancellor, Marc Rubinstein
Summary
The weekly wrap tied together four interviews around a single question: whether today’s market is being distorted by a bubble regime, and what that means for investors. Jeremy Grantham argued that the megacap winners may be benefiting from durable monopoly power, not just better execution, and that AI is likely to become a cost of doing business rather than a lasting boost to aggregate profits. He also warned that policy restraint on market concentration has been unusually weak, allowing dominant firms to keep compounding.
Andy Constan laid out his bubble framework: something new, an escalation phase, and then a peaking phase that can last a long time but is hard to time. He linked past episodes to technology, deregulation, housing, and policy easing, and said today’s AI boom fits the same pattern even if the exact end point is unknowable. Edward Chancellor added that capex booms can temporarily inflate reported profits, but those profits reverse when investment is misallocated and depreciation catches up.
Marc Rubinstein took the other side of the risk debate on private credit, arguing the hazards are real but probably not systemically catastrophic unless they combine with something else. The broader message was that today’s market is being driven by powerful narratives, huge capital spending, and confusing crosscurrents in financials, Europe, and AI.
Key takeaways
- Grantham argued that the Mag 7 may have escaped normal competitive pressure because software and lax antitrust policy have allowed near-monopolies.
- Constan said bubbles usually begin with “something new,” then move through escalation events before entering a peaking phase that can last much longer than investors expect.
- Chancellor warned that capex booms can make profits look stronger at first, but profitability can collapse once investment proves misallocated and depreciation rises.
- Rubinstein said private credit risks are real, especially with retail ownership and redemption gates, but likely need a second shock to become systemic.
- Grantham said AI may raise early-adopter margins temporarily, but eventually it should settle into a normal business cost rather than a permanent profit engine.
Notable quotes
“It is now in that point in the future the cost of doing business. It will not move aggregate profit margins or aggregate profits notably higher than they are typically”
“These types of environments typically start with something new. And something new in the internet boom and the um and if we're in a bubble today uh the AI boom”
“So the profit margins of the monopouists go up, the share going to workers goes down, inequality increases, but the growth rate of the GDP tends to slow down”
“One of the features of the of the capex booms is is that they as you know they they actually produce profits”
“the amount of money ultimately that's invested in private credit on terms that limit redemptions is tiny in the context of the overall financial system”
How the episode opens
Fast forward a few years. Everybody is doing AI, aren't they? Everybody is paying for the service that they need. It is now in that point in the future the cost of doing business. It will not move aggregate profit margins or aggregate profits notably higher than they are typically.
Not only did they cut, but they did surprise cuts. And this is from the same guy who, you know, 40% ago had used the term irrational exuberance to describe the stock market. He was cutting into a stock market that was up 40% from when he made those comments.
One of the features of the of the capex booms is is that they as you know they they actually produce profits because if someone invests and the other person the buyer doesn't actually immediately depreciate what they're uh what what they've acquired then um they um then aggregate profits rise.
Welcome to the excess returns weekly rap. I'm Jack Forehand, joined as always by my good friend Matt Ziggler. Matt, we got we got some pretty good clips this time. — I am I mean I just can't believe like Jeremy Grantham. This is this is a mur I feel like we say this every week right now. This is like a murderer row of like holy crap going through this and I'm going I am embarrassed by how many cool people we've had on Access Returns this week.
Yeah, Grant's somebody we've like when you start a podcast he's one of the people like you're like I want to get him on eventually. Like we're six years in now and we got him. So, uh, that that was kind of fun. He he was a really nice guy. It was a lot of fun to do that one.
From the episode’s captions: roughly the first two minutes, lightly cleaned. Keep watching on YouTube →
Topics
- ai investment bubble
- mean reversion
- private credit
- financials and european banks
- market concentration and monopoly power
Watch the episode
Summary, takeaways and quote selection by Octagon. Quotes are short excerpts; the full conversation is in the episode.
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