The Big Short’s Michael Berry Called Index Funds a Bubble. Here’s What the Record Shows
Michael Burry called index funds a bubble and predicted an ugly crash. Seven years later, the money that stayed invested tells a complicated story, and the part of his warning that still stands is sitting inside your retirement account right…
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In a Bloomberg email interview published Sept. 4, 2019, Michael Burry compared the flood of money into index funds to the pre-2008 bubble in collateralized debt obligations. Burry is the investor whose short position against subprime mortgage bonds inspired The Big Short. His warning was blunt: “Like most bubbles, the longer it goes on, the worse the crash will be.”
That was 7 years ago, and the stakes are personal. The S&P 500 index fund is the core holding in millions of retirement accounts. If Burry was right, those savers own a flawed product. If he was wrong, anyone who left index funds over his warning paid for it.
As a reason to sell, the bubble call failed. His point about concentration is still open, and you can measure it in your own fund today.
How Passive Money Can Bend Stock Prices
Burry argued that “passive investing has removed price discovery from the equity markets.” Price discovery is how a stock finds its fair value. Buyers and sellers study earnings, argue over what the business is worth and push the price toward that number.
An index fund skips all of that. When a dollar reaches the Vanguard S&P 500 ETF (NYSEARCA:VOO), the fund buys every stock in the index in proportion to its market value. It never asks whether a stock is cheap or expensive. As a company gets bigger, it takes a bigger share of every new dollar.
The worry holds together. Burry said CDO prices were set “by massive capital flows” instead of security-level analysis. If enough investors stop analyzing and simply follow the money, prices can drift away from fundamentals. He warned that when the flows reverse, “it will be ugly.”
What $10,000 Did After the Warning
Look at the window right after the interview, from Sept. 3, 2019 through this week. Over that period, VOO returned 198% on a dividend-adjusted basis. That turns $10,000 into roughly $29,782.
The SPDR S&P 500 ETF (NYSEARCA:SPY) gained 167% over the same period. That number covers price only and leaves out dividends, which is why it trails VOO’s adjusted figure. Both funds hold the same index.
Berkshire Hathaway (NYSE:BRK-B | BRK-B Price Prediction) is the best-known example of active capital allocation, and it returned 152%. That works out to about $25,199 on the same $10,000. Over the past year, Berkshire gained about 1% while VOO rose 17%.
A bubble warning that stays wrong for seven years, while the supposedly trapped investors triple their money, has failed as a timing signal. Burry’s defenders would point back to his own words: the longer it runs, the worse the crash. Riding a mania while planning the exit is its own discipline, and we put both halves in a free handbook on surviving bubbles. That argument leads straight to the part of his case the record has not settled.
Concentration Is the Risk Still on the Table
SPY’s March 2026 fact sheet shows its top 10 holdings at about 36% of assets. Alone, NVIDIA (NASDAQ:NVDA) makes up 8%. Apple (NASDAQ:AAPL) adds 7%.
Vanguard’s June 2026 report shows VOO held 519 stocks. Information technology made up 38% of net assets. So you own a 500-stock fund, yet more than a third of each dollar sits in 10 companies. A bad earnings period at two or three of them would hit the whole fund.
Burry described exactly this mechanism. Cap-weighting sends new money toward whatever has already gone up. For his warning to look right in the end, two things would likely have to happen together. Index inflows would need to turn into steady outflows, for example as retired people draw down their accounts. At the same time, the largest holdings would need to miss on earnings. Until both happen, concentration is a risk you can measure, and the crash is still only a guess.
3 Checks to Run on Your Index Fund This Week
1. Find your top-10 weight: Every fund fact sheet lists it. For SPY it is about 36%. If you also own individual tech stocks, add them in. You may hold far more of the same few companies than you think.
2. Compare expense ratios in dollars: VOO charges 0.03%, which is about $3 a year per $10,000. SPY charges about 0.09%, or roughly $9. Both buy the same index, so the cheaper fund keeps more of the return.
3. Write down a rebalancing rule: One example would be the following. Once a year, if stocks have drifted more than five percentage points above your target allocation, sell back to target. This does at the portfolio level what cap-weighting never does, which is trim whatever has grown the most.
Contact [email protected] for any questions or corrections.
Joel South covers large-cap stocks, dividend investing, and major market trends, with a focus on earnings analysis, valuation, and turning complex data into actionable insights for investors.
He brings more than 15 years of experience as an investor and financial journalist, including 12 years at The Motley Fool, where he served as an investment analyst, Bureau Chief, and later led the Fool.com investing news desk. He has also co-hosted an investing podcast and appeared across TV and radio discussing market trends.
