The Passive Investing Bubble Myth: Is Too Much Money in Index Funds Breaking the Market?

I was at a barbecue last summer when it happened again.

A friend of a friend – let’s call him Derek – found out I invest almost entirely in index ETFs. He got this look on his face like I had just told him I leave my front door unlocked at night. “You know passive investing is a bubble, right?” he said, holding his beer with the confidence of someone who had watched one Michael Burry interview. “When everyone just blindly buys the same index, it inflates prices and kills price discovery. The whole thing is going to collapse eventually.”

Derek was not some crank. He’s a smart guy with a good career. He had clearly read some articles. And honestly, I used to have the same worry. A few years ago, when I first started buying XEQT every month, I remember lying awake one night wondering: what if all these people buying index funds really are creating a massive bubble? What if I’m the sucker pouring money into an overinflated system?

So I did what I always do when something scares me about investing. I went looking for the actual data. I read the academic research. I looked at the numbers. And what I found was that the “passive bubble” argument, while intellectually interesting, falls apart almost completely when you examine it closely.

The fear that too many people buying index funds is breaking the stock market is one of those ideas that sounds smart at a cocktail party but does not survive contact with evidence. Let me walk you through why.

1. What Critics Actually Claim

Before I debunk anything, let me steelman the argument. The “passive investing bubble” thesis has been put forward by some genuinely credible voices, and it deserves a fair hearing.

Michael Burry – the “Big Short” guy who correctly predicted the 2008 mortgage crisis – compared index fund investing to the synthetic CDOs that blew up the financial system. In a 2019 Bloomberg interview, he argued that the flood of money into passive funds was inflating the prices of stocks included in popular indexes, regardless of their fundamentals.

Several prominent hedge fund managers, including Inker of GMO and executives at various active management firms, have argued that passive investing is creating a “free rider problem.” Their claim: active managers do the hard work of analyzing companies and setting prices, while passive investors just piggyback on that price discovery without contributing to it. If too many people free-ride, the system breaks.

The core argument boils down to three claims:

1. Index funds buy stocks blindly. They purchase every company in the index proportionally, regardless of whether a stock is overvalued or undervalued. This drives up prices indiscriminately.
2. Price discovery is being destroyed. As more money flows into passive funds, fewer investors are doing fundamental analysis. Eventually, stock prices will no longer reflect reality.
3. This creates bubble-like conditions. Stocks are being bid up simply because they are in an index, not because they are good businesses. When the music stops, the crash will be catastrophic.

If this were true, buying XEQT every month would basically be contributing to a ticking time bomb. That is a scary thought. So let’s see if the evidence supports it.

2. Why the Bubble Argument Falls Apart

Here is the thing Derek and Michael Burry’s followers tend to miss: the passive investing bubble narrative rests on several assumptions that are either wildly exaggerated or simply wrong.

Active Trading Still Dominates Volume

This is the single most important fact in this entire debate, and most people get it backwards.

Yes, passive funds have grown enormously. But passive investors are not the ones setting prices on a daily basis. Price discovery happens through trading – the buying and selling that occurs throughout each trading day. And the vast majority of that trading is done by active participants: hedge funds, algorithmic traders, proprietary trading firms, institutional investors, and yes, individual stock pickers.

Research from Bernstein and other firms has estimated that passive funds account for only about 5-10% of daily equity trading volume in the United States. The rest is active. Even though passive funds hold a significant share of total assets, they trade infrequently – that is the whole point of passive investing. You buy and hold. You are not the one sitting there all day moving prices.

So when Derek says “everyone is just blindly buying the index,” what he really means is that a growing number of people are parking long-term savings in index funds and then mostly leaving them alone. The actual minute-by-minute, hour-by-hour process of price discovery is still overwhelmingly driven by active traders.

Passive Is Still a Minority of Total Assets

Despite the dramatic growth of index funds, passive investing is not as dominant as headlines suggest. Depending on how you measure it, passively managed funds hold somewhere between 25% and 40% of total equity market capitalization globally.

That means the majority of all invested capital is still actively managed. Pension funds, sovereign wealth funds, hedge funds, insurance companies, family offices, and millions of individual stock pickers are all still making active decisions every day. The idea that passive investing has “taken over” is simply not supported by the numbers.

The Market Is Self-Correcting

This is the part that really kills the bubble argument. Let’s imagine, hypothetically, that passive investing did grow so large that it created meaningful mispricings in the market. What would happen next?

Active managers would exploit those mispricings. If a company’s stock price were inflated purely because it was in the S&P 500 index, smart active traders would short that stock and profit when it corrected. If a company outside the index were undervalued because passive flows were ignoring it, active managers would buy it at a discount.

In other words, the more passive investing distorts prices, the more profitable active management becomes. This attracts more capital back into active strategies, which corrects the distortion. The market has a built-in thermostat. It is self-regulating.

Economists call this the Grossman-Stiglitz equilibrium: markets need some amount of active management to function, and as long as there are profits to be made from active analysis, someone will always step in to do it. The system does not require everyone to be active. It just requires enough active participants – and we are nowhere near the danger zone.

3. Active vs Passive: How Big Is Passive Really?

Let’s look at the actual numbers on the growth of passive investing. These figures will help put the “bubble” hysteria in perspective.

Look at that third column. Even as passive fund assets have nearly quadrupled over the past 20 years, passive trading volume as a share of total daily volume has barely budged. That is because passive funds trade so infrequently – they mostly just buy on inflows and sell on redemptions.

The heavy lifting of price discovery is still being done by active traders. The idea that XEQT investors buying $500 a month are somehow overpowering the hedge funds and algorithmic traders that move billions of dollars every day is, frankly, laughable.

4. The Price Discovery Myth

Let me address this one directly, because it is the strongest version of the passive bubble argument.

Price discovery is the process by which stock prices come to reflect available information about a company’s value. When an analyst reads an earnings report, builds a model, and decides a stock is undervalued, they buy it, pushing the price up toward its “fair” value. When bad news comes out, traders sell, pushing the price down. This continuous process of analysis, trading, and price adjustment is what keeps markets functioning.

The concern is: if passive investors don’t do any of this analysis, and they just buy everything in the index, are they degrading the quality of price discovery?

Here is why this concern is overblown.

Passive Funds Don’t Need to Do Price Discovery

The whole beauty of passive investing is that you are free-riding on the price discovery that active traders do – and that is perfectly fine. It is not cheating. It is not exploiting a loophole. It is simply accepting that the collective wisdom of millions of active traders has already incorporated available information into stock prices.

Think of it this way. When you drive on a highway, you benefit from all the engineers who designed the road, the construction workers who built it, and the government inspectors who maintain it. You don’t need to understand civil engineering to use the road safely. Similarly, when you buy XEQT, you benefit from the millions of active market participants who have already set prices through their analysis and trading. You don’t need to replicate their work.

Academic Research Supports This

A 2021 paper by researchers at UCLA and the London Business School examined whether the rise of passive investing had degraded price efficiency. Their findings? Stock prices had not become less informationally efficient despite the massive growth of index funds. If anything, some measures of price efficiency had improved, because the remaining active traders had become more sophisticated and better resourced.

Other research from the National Bureau of Economic Research (NBER) has reached similar conclusions. The shift toward passive investing has not noticeably impaired the market’s ability to incorporate new information into prices.

Why? Because price discovery does not require a large number of participants. It requires a sufficient number of motivated, well-resourced participants. And there are plenty of those. Thousands of hedge funds, quantitative trading firms, and institutional investors are actively hunting for mispricings every day. They have more data, faster computers, and better models than at any point in history. The ecosystem of active price discovery is alive and well.

5. What Would an Actual Passive Bubble Look Like?

Okay, so what if the critics are right eventually? What would the world actually look like if passive investing truly broke the market?

Here are the conditions that would need to exist:

• The vast majority (80%+) of all invested capital would be passive. We are currently at roughly 35-38%. We would need to more than double passive market share before this became a theoretical concern.
• Stock prices would become completely disconnected from fundamentals. Terrible companies would trade at the same valuation multiples as great companies, simply because they are in the same index. We do not see this happening. Stock prices still react dramatically to earnings reports, management changes, and other fundamental news.
• Active trading volume would dry up. If nobody were doing price discovery, bid-ask spreads would widen, volatility would increase during new information events, and markets would become visibly dysfunctional. None of this is happening. Spreads are tighter than ever, and markets react to news faster than ever.
• Active managers would be consistently outperforming. If passive investing were truly distorting prices, active managers who do fundamental analysis should be cleaning up – finding and exploiting those distortions. Instead, the SPIVA data shows that active managers continue to underperform at the same miserable rate they always have. If anything, their performance has gotten worse, not better, which is the opposite of what you would expect if passive investing were creating exploitable inefficiencies.
• Small-cap and off-index stocks would be dramatically undervalued. If index inclusion were artificially inflating prices, stocks outside the major indexes should be trading at significant discounts. While there is some evidence of modest index inclusion effects, there is no evidence of a broad, systematic undervaluation of non-index stocks.

None of these conditions exist today. Not one. The passive investing bubble is a hypothetical scenario for a world that bears no resemblance to the one we actually live in.

6. The Real Bubble Is in Fees

You want to know what actually looks like a bubble? The Canadian mutual fund industry.

For decades, Canadians have been paying some of the highest investment management fees in the developed world. The average Canadian equity mutual fund still charges an MER of roughly 2.0% to 2.5%. That is 10 to 12 times what XEQT charges at 0.20%.

And what do investors get for paying those fees? According to the SPIVA Canada scorecard, roughly 90% of actively managed Canadian equity funds underperform their benchmark index over a 10-year period. You are paying more for worse results.

Let me show you what this fee “bubble” actually costs a Canadian investor over a lifetime.

Cost Comparison: XEQT vs Active Mutual Fund Over 25 Years

Assumptions: $500/month contribution, 7% gross annual return, fees deducted annually.

Look at that fees row. The mutual fund investor pays roughly $73,000 in fees over 25 years. The XEQT investor pays about $9,400. That $63,600 difference in direct fees, combined with the lost compounding on that money, results in a total wealth gap of approximately $122,000.

That is the real bubble. Not a hypothetical bubble in index fund prices – a very real, very measurable bubble in the fees that the Canadian mutual fund industry extracts from ordinary investors every single year.

When Michael Burry or some hedge fund manager warns you about the dangers of passive investing, ask yourself: who benefits from scaring you away from a 0.20% MER product and back toward a 2.10% MER product? The answer is not “you.”

7. Why This Argument Keeps Coming Back

If the passive bubble argument is so weak, why does it keep resurfacing? Why does it get so much media coverage? Why does some version of it show up in my comments section every few months?

The answer is incentives.

Active Managers Have Everything to Lose

The multi-trillion-dollar active management industry is watching its business model die in slow motion. Every dollar that flows into XEQT is a dollar that does not flow into a managed fund charging 1-2% in fees. Every investor who figures out that passive investing has won is a client that an active manager loses – probably forever.

What do you do when your business is under existential threat? You find reasons why the alternative is dangerous. “Index funds are a bubble” is the most effective scare tactic the active management industry has ever come up with. It sounds sophisticated. It references legitimate economic theory (the Grossman-Stiglitz paradox). It even has a celebrity spokesperson in Michael Burry. It is the perfect piece of marketing dressed up as market analysis.

I am not saying every person who raises this concern has bad intentions. Derek at the barbecue was genuinely worried. But the reason this argument exists in the cultural water supply is that very wealthy, very motivated people in the financial industry have spent a lot of time and money promoting it.

The Media Loves a Contrarian Story

“Passive investing is working great and you should keep doing it” does not generate clicks. “Is passive investing a ticking time bomb?” does. Every financial publication in the world knows that fear drives engagement, and the passive bubble narrative is perfect fearmongering material. It takes a nuanced academic concept, strips away the nuance, and presents it as an imminent threat to your savings.

Whenever you see one of these articles, check the byline. Often it is written by someone affiliated with the active management industry, or it quotes sources who are. The story writes itself because the people with the most to lose are the most willing to talk.

Complexity Bias Makes It Stick

There is a psychological phenomenon where people instinctively believe that complex explanations are more likely to be true than simple ones. The passive bubble argument is complex. It involves concepts like price discovery, market efficiency, index inclusion effects, and the Grossman-Stiglitz paradox. It feels like a sophisticated insight.

Meanwhile, the counterargument is simple: most active managers can’t beat the index after fees, so just buy the index. Simple truths are easy to dismiss because they don’t feel clever enough.

But in investing, simple almost always wins. Dollar-cost averaging into XEQT every month is boring. It is not going to make you the most interesting person at the barbecue. But it is going to make you wealthier than Derek over the next 30 years, and you won’t have to lose a single night of sleep over phantom bubbles.

8. The Bottom Line

The passive investing bubble myth is a sophisticated-sounding argument that does not survive scrutiny. Here is what you need to remember:

• Active trading still dominates daily volume. Passive funds hold a growing share of total assets but account for only a small fraction of daily trading. Price discovery is alive and well.
• Passive is still the minority. At roughly 35-38% of global equity assets, passive investing is far from the levels that would theoretically threaten market efficiency.
• The market self-corrects. If passive investing ever did create meaningful mispricings, active managers would exploit them, attracting capital back to active strategies. The system has a built-in thermostat.
• Academic research shows no degradation in price efficiency. Despite massive growth in index funds, stock prices continue to react to fundamental information the way they should.
• The real bubble is in fees. Canadians paying 2%+ MERs on mutual funds are losing six figures over a lifetime. That is a far more immediate and measurable problem than any hypothetical index fund distortion.
• The people promoting this narrative have financial incentives to do so. Active managers who are losing assets to passive funds benefit directly from scaring investors away from index products.

I think about Derek sometimes. He is a smart, well-intentioned person who genuinely believes he is seeing something that passive investors are missing. But the data does not support his concern – not yet, and likely not for decades, if ever. Meanwhile, every month he spends worrying about a phantom bubble is a month he could have been quietly building wealth in a globally diversified, ultra-low-cost ETF.

If you are investing in XEQT through Wealthsimple, you are not contributing to a bubble. You are buying a tiny slice of over 9,000 companies across 49 countries, benefiting from automatic rebalancing and a transparent, rules-based methodology, all for a fraction of the cost of the alternative. You are doing exactly what the evidence says you should do.

The passive investing bubble is a myth. The fee bubble is real. Focus on the one that actually costs you money.

Disclosure: This post contains referral links. I may receive compensation if you sign up through these links, but this does not affect my honest assessment. I genuinely believe XEQT is an excellent choice for Canadian investors seeking simple, low-cost, globally diversified growth. This is not financial advice.