There’s a version of this story where everything is fine. Corporate earnings are strong, balance sheets are clean, and a generation of new investors has finally gotten access to the same tools that institutions have used for decades. Sixty-two percent of American adults now own stocks, according to Gallup, and US households have 48% of their assets in equities — the highest allocation since the dot-com peak in 2000. You could read that last sentence two very different ways, and I think both readings are correct.
Let me start with the legitimate case, because it deserves a fair hearing. Vanguard has argued that innovation, productivity, favorable regulation, and strong corporate balance sheets can partly justify elevated prices. Heritage Consultants noted that higher valuations can be rational in environments with low or falling interest rates, low inflation, or strong earnings growth. That’s not spin — it’s how discounting works. A dollar of future earnings is worth more when the rate you use to discount it is lower. And the companies dominating today’s indices are not the smoke-and-mirror dot-coms of 1999; they generate real cash, buy back real shares, and have real pricing power. Critics of the Shiller CAPE ratio — the cyclically adjusted price-to-earnings measure that compares current prices to average inflation-adjusted earnings over the past decade — have a point when they note, as Aptus Capital Advisors did, that it fails to account for share buybacks, changing market composition, and today’s structurally higher profit margins. Fisher Investments put it more bluntly: CAPE is stuck in the 20th century, using old information to forecast forward-looking markets. I don’t fully agree, but I understand the argument.
Here’s where I start getting uncomfortable.
The same data that tells the optimistic story also tells a cautionary one. US ETF inflows hit a record $1.49 trillion in 2025, with passive equity ETFs alone pulling in $638 billion, according to FactSet. Retail investors poured a record $308 billion into US stocks that year, running $5.4 trillion in total trading activity across stocks and ETFs, per Fortune. Retail investors accounted for roughly 20% of US stock market trading volume in Q3 2025 — the second-highest level on record. That’s not democratization as a side story anymore. That’s the market microstructure — the actual mechanics of how prices get set — being reshaped in real time. When passive funds collectively hold that much of the market and trade primarily at closing auctions to match NAV, and when retail participants are simultaneously herding based on social media signals rather than fundamental analysis, you have a system where price discovery — the process by which markets establish fair value — is operating under genuinely novel conditions. Whether those conditions are stable is the question I keep turning over.
The history here is not subtle. Retail herding into speculative assets via easy access has a remarkably consistent ending. The Dutch traded tulip futures at prices equivalent to luxury houses in 1637, then watched prices fall 95–99% in weeks. South Sea Company stock went from £128 to over £1,000 in six months in 1720, then collapsed to £150 by December, bankrupting thousands of ordinary investors who had borrowed to buy shares. The 1929 crash arrived after retail investors had driven margin borrowing to 90% of purchase price; what followed was an 89% decline in the Dow over three years. The dot-com bubble is the most recent rhyme — NASDAQ fell 78% between 2000 and 2002, and most of the retail accounts opened in the late 1990s frenzy were wiped out or permanently impaired. I am not predicting any of those outcomes now. I am pointing out that the mechanism — easy access, social coordination, herding into momentum, a narrative that justifies any price — is not new, even if the technology delivering it is.
GameStop is the case study that most people have already absorbed, but I think they’ve drawn the wrong lesson from it. The popular read is that retail beat Wall Street that one time, in January 2021, when coordinated buys on r/WallStreetBets drove GME from roughly $17 to an intraday peak of $483, costing short sellers over $5 billion. Keith Gill, posting under Roaring Kitty, turned a $53,000 position into $48 million. He later testified to Congress, famously saying “I like the stock.” What gets less attention is the collapse to $40 by February, and who held the bag. Academic research published in the Journal of Financial Stability found that retail herding like this intensifies the impact of crises, creates excess volatility, and increases the fragility of the financial system. A separate paper in the Review of Financial Economics specifically cited GameStop as a case study in how coordinated retail buying can become the source of risk shocks for institutional investors — which sounds like a victory until you notice that fragile systems don’t just hurt the people on the other side of the trade.
The honest counter-argument is that this fragility hasn’t broken anything yet. Markets recovered from 1987’s Black Monday within two years. The circuit breakers installed after that crash did their job. Goldman Sachs, assessing conditions in 2025, noted that global equities show “some characteristics of an early-stage bubble, such as valuation excess, concentration, and investor exuberance” — but stopped short of calling it one, arguing the fundamentals aren’t yet detached enough. Brucewood Capital’s analysis of the Shiller CAPE found that when CAPE exceeds 37, the average 10-year cumulative price return is -4.7%, with returns landing in the green only 29% of the time — a troubling statistic, but a 10-year horizon is cold comfort if you’re not planning to sell for 10 years. And passive investing, as BlackRock’s Larry Fink has noted, is often misunderstood: index funds trading at closing auctions aren’t the same as momentum chasers. There’s real discipline baked into the structure, even if the aggregate flows are enormous.
What changes my read on all of this is the combination, not any single factor. Passive flows at record scale compress the price signals that active managers use to identify mispricing. Retail herding via social media operates faster than any regulatory response and with less friction than any previous era of retail speculation. Household equity allocations at 48% of assets — levels last seen at the dot-com peak — mean the average investor has less cushion than usual if prices correct sharply. None of these individually is a crisis. Together, they describe a market that is more reflexive, more sentiment-driven, and more tightly coiled than the structural-change story alone would suggest.
If I were to state what would change my mind: if corporate earnings continue to grow at high single digits annually for the next three years while the CAPE ratio gradually compresses through earnings expansion rather than price decline, the structural bulls will have been right and I will have been too cautious. I can live with that outcome.
What I can’t quite shake is a simpler observation. Every generation of retail investors entering the market in large numbers has believed — usually with some justification at the time — that this cycle was different from the last one. They were right about the justification and wrong about the cycle.