Episode summary
The "AI Bubble" and Stock Market Concentration | Rational Reminder 390
The Rational Reminder Podcast
· · 1 hr 20 min · Hosts: Benjamin Felix, Ben Wilson, Dan Bortolotti
Summary
The episode argues that the bigger issue in today’s U.S. market is elevated valuation, not concentration by itself. The hosts focus on the “Magnificent 7,” which now make up 36% of the S&P 500 and 32% of the U.S. total market, and note that this is the most extreme concentration in U.S. market history going back to 1927. But they also emphasize that concentration alone has a weak historical link to future returns, while high valuations have a much clearer relationship to lower long-run returns.
They frame the current AI surge as a familiar pattern: revolutionary technology, huge capital spending, rising stock prices, speculation, and then often a painful unwind. Even so, the hosts stress that bubbles can be economically productive because cheap capital helps build real infrastructure, as happened with railroads and the internet. The danger is mainly for investors who buy near the top, not necessarily for the economy as a whole.
The discussion leans heavily on historical examples: Nortel in Canada, the U.S. dot-com bust, and Japan’s 1989 peak. In each case, globally diversified investors and value stocks weathered the damage better than concentrated investors. The main prescription is not market timing, but discipline, diversification, and tempered return expectations when valuations are high.
Key takeaways
- The hosts say U.S. market concentration is extreme, but history suggests valuation matters more than concentration for future returns.
- They argue the current AI boom may resemble past technology bubbles that helped build real infrastructure while hurting late-cycle investors.
- They cite Nortel, the dot-com bust, and Japan as examples showing that single-country concentration can look safe right up until it isn’t.
- They say value and small-cap value stocks often held up better than the broad market during past bubble unwinds.
- Their practical advice is to stay diversified globally and avoid trying to time a possible bubble burst.
Notable quotes
“36% of the S&P 500 consists of just seven stocks”
“Market concentration and future returns has a really noisy relationship if there's any relationship at all”
“bubbles are super exciting on the way up that often inducing FOMO”
“diversification means that you always hold the winners and the losers”
How the episode opens
This is the Rational Reminder podcast, a weekly reality check on sensible investing and financial decision-making from three Canadians. We're hosted by me, Benjamin Felix, chief investment officer, Dan Bordalotti, portfolio manager, and Ben Wilson, head of M&A at PWL Capital.
Happy New Year, everyone. — Yeah, welcome to the first episode of 2026. I I wanted to — Episode 390. It's crazy. Almost 400 episodes.
Yeah, that is that is crazy. We have some great guests planned for we've we've already got guests booked until uh I don't know, March or April of of this year. And some some great great guests, which I think will be uh it'll be good as always.
Um, I I wanted to take a minute at the beginning of this episode to talk about the podcast for a second. Uh, as we say in the introduction, this podcast is aimed at promoting the principles of sensible investing and financial decision-m for anybody. We used to say in the intro that it was for Canadians, but we had uh people who were from places other than Canada give us the feedback that it was alienating.
So, we we changed it to from three Canadians. Uh anyway, so we we are Canadian, but the podcast content tends to be globally applicable. Uh the hosts, which it's the three of us today, as I mentioned in the introduction.
Uh we also have Cameron Passmore who who co-hosts occasionally. He used to be the main co-host with me, but that's changed over time. All of us are employees of PWL Capital which is a Canadian wealth management firm that uses lowcost investment products uh meaning lowcost index funds or funds from a company called dimensional fund advisors.
And we also emphasize the intersection of financial planning and sensible portfolio management as opposed to doing either one of those things in isolation.
From the episode’s captions: roughly the first two minutes, lightly cleaned. Keep watching on YouTube →
Topics
- ai bubble
- stock market concentration
- market valuations
- market euphoria
- diversification
Companies and tickers mentioned
- Nortel
Watch the episode
Watch “The "AI Bubble" and Stock Market Concentration | Rational Reminder 390” on YouTube
Summary, takeaways and quote selection by Octagon. Quotes are short excerpts; the full conversation is in the episode.
More from The Rational Reminder Podcast
-
Wealthy People Are Hiding in Plain Sight (ft. Owen Zidar) | Rational Reminder 428 -
What to Know Before (and After) You Hire an Advisor (with Matthew Taylor) | Rational Reminder 427 -
The Finances of Marriage | Rational Reminder 426 -
The Ethics Problem in Financial Services (Dr. Moira Somers & Philippa Hann) | Rational Reminder 425 -
50 Years of Evidence-Based Investing (with David Booth) | Rational Reminder 424 -
The Future of AI in the Workplace | Special Episode (Mike Sullivan and Vinay Gidwaney)
The Rational Reminder Podcast, this episode and its artwork belong to Benjamin Felix, Cameron Passmore, and Dan Bortolotti. Octagon is not affiliated with the show; this page is an independent summary.
