The Effects of ETF Investing on Financial Markets

How ETF Investing Is Changing Market Dynamics

Author

Nam Nguyen
August 23, 2026 • Estimated Reading Time: 5 minutes

Market dynamics are changing rapidly. For example, we recently discussed how the growth of retail options trading is changing market dynamics. At the same time, passive investing, largely through ETFs, has grown substantially over the past decade. In today's edition, we discuss how ETF investing is changing market dynamics as well.

In this issue:

Latest Posts

  • Market Regimes and Changing Market Dynamics (10 min)

  • Making Option Pricing Models More Practical (10 min)

  • Algorithmic Trading, HFT, and Market Stability (10 min)

  • The Market Impact of Retail Options Trading (10 min)

  • Why System Validation Matters More Than Ever (10 min)

Upcoming Conferences

  • The CBOE Quant Conference is a gathering of thought leaders from academia and industry to examine the future of quantitative finance. This year, they feature fantastic speakers such as Emanuel Derman and Fabio Mercurio. If you're a member of an academic institution, you can receive a substantial discount. Follow the link below for more details

  • I will be speaking at the Future Alpha Conference next March. The topic is still being determined, but the discussion will focus on risk management, AI, and machine learning. Stay tuned for more details.

The Impact of Passive ETF Ownership on the Market

Passive investing, particularly through Exchange-Traded Funds (ETFs), has transformed the world of finance. With ETFs, investors can gain exposure to various asset classes, including stocks, bonds, commodities, and more, while maintaining a passive and diversified approach to their portfolios. Unlike actively managed funds, which aim to outperform the market, passive investing with ETFs seeks to replicate the performance of an underlying index. This approach often comes with lower fees and can be an alternative choice for long-term investors looking for broad market exposure and reduced stock-specific risk. The ease of buying and selling ETFs on stock exchanges makes them a flexible tool for building a well-diversified, cost-effective investment portfolio, appealing to both individual investors and institutions.

While ETFs offer various advantages, their impact on the market has raised questions about potential negative effects. Reference [1] delved into this very issue, investigating the market repercussions of ETFs.

Findings

  • The study finds that higher passive ETF ownership leads to stronger and more persistent return reversals.

  • Higher passive ownership is associated with wider bid-ask spreads, greater exposure to aggregate liquidity shocks, higher idiosyncratic volatility, and greater tail risk.

  • The results show that passive ETF ownership reduces the importance of firm-specific information in stock returns.

  • Higher passive ownership increases the importance of transitory noise and exposure to market-wide sentiment shocks.

  • The study finds that increased passive ETF ownership reduces stock price informativeness and potentially weakens market efficiency.

  • The findings highlight a potential trade-off between the benefits of passive investing and the costs of reduced price efficiency and market-making capacity.

Briefly, an increase in passive ETF ownership results in stronger and longer-lasting return reversals, greater idiosyncratic volatility, and elevated tail risk. Higher passive ETF ownership reduces the significance of firm-specific information for returns while increasing sensitivity to transitory noise and market-wide sentiment shocks.

Reference

[1] Höfler, Philipp and Schlag, Christian and Schmeling, Maik, Passive Investing and Market Quality (2023). SSRN 4567751

Price Fragility, ETF Flows, and Non-Fundamental Shocks

Financial asset fragility refers to the vulnerability of an asset’s price to sudden and disproportionate changes in response to shocks, even if those shocks are relatively small. This fragility often stems from factors like excessive leverage, crowded positioning, liquidity mismatches, or overreliance on certain market assumptions.

Reference [2] utilized the concept of stock price fragility to study the impact of ETFs on the market. Stock fragility is derived from information on an asset’s ownership composition, combined with data on the correlation between owners’ non-fundamentally driven trades.

The paper generalizes mutual fund (MF) fragility to ETF fragility because it argues that ETF flows are indicative of non-fundamental demand shocks. Theoretically, the creation and redemption of ETF shares mimic relative mispricing correction. Therefore, ETF premiums or discounts (i.e., relative mispricing) signal non-fundamentally driven price distortions.

Findings

  • The study proposes an ETF-based measure of stock price fragility as an alternative to traditional measures based on equity mutual fund flows.

  • The ETF-based measure significantly improves the ability of stock price fragility to predict future stock return volatility.

  • The study finds that the explanatory power of mutual fund-based fragility has declined.

  • The ETF-based measure partially captures the effect of institutional ownership on stock price volatility.

  • The predictive power of ETF-based fragility for next-quarter stock price volatility is primarily driven by active ETFs.

  • The study notes that the distinction between passive and active investing has become increasingly blurred as the ETF industry has evolved.

  • Specialized, industry-specific, and characteristic-based active ETFs may reflect investors’ extrapolative beliefs, speculative demand, and sentiment-driven demand.

In summary, the article developed the concept of ETF fragility and showed that active ETFs have an impact on the market.

This is an interesting article, as it quantifies the concept of fragility. This concept can be further applied to study, for example:

  • The impact of income ETFs (those that sell options) on the market

  • Whether a price gap is filled, if it’s fundamentally induced or just the result of a demand shock.

Reference

[2] H. Galindo Gil and R. Lazo-Paz, An ETF-based measure of stock price fragility, Journal of Financial Markets 72 (2025) 100946

Closing Thoughts

Together, these studies highlight how the growth and evolution of ETFs can affect stock prices and market dynamics. Higher passive ETF ownership is associated with reduced price informativeness, greater non-fundamental noise, higher volatility, and increased tail risk, while the second study shows that ETF-based measures of stock price fragility can better capture and predict these effects, particularly through active ETFs.

Overall, the findings suggest that ETF ownership and flows have become increasingly important factors in understanding stock price volatility and market efficiency.

Additional Reading

For further discussion on changing market dynamics, refer to the previous issues:

Educational Video

In this video, Professor Itzhak Ben-David explains that ETFs have grown rapidly because they provide liquid, inexpensive, and easily accessible exposure to portfolios of securities. However, he draws an important distinction between broad-market and specialized ETFs. Specialized ETFs are often launched in areas already experiencing strong investor demand, such as Bitcoin or AI. Because launching an ETF can take six to nine months, these products may reach the market when valuations in the targeted niche are already elevated. His research finds that specialized ETFs tend to underperform during the first few years after launch, suggesting that ETF launches can sometimes serve as an indicator of overvaluation and speculative activity in a particular market segment. 

More importantly, Ben-David discusses how ETF investing can affect the pricing of the underlying securities. ETFs attract new investors and lower barriers to market participation, but demand shocks originating in the ETF market are transmitted to the securities held by the ETF as the fund acquires those assets. According to Ben-David, this mechanism can make underlying security prices less informative, more volatile, and noisier. Toward the end of the discussion, he highlights another evolution in the industry: the rapid growth of actively managed ETFs and continued product innovation around popular themes such as crypto and AI. The broader implication is that ETFs are not merely passive vehicles that reflect prices in underlying markets; their growth, investor flows, and product design can themselves influence market pricing and dynamics. 

Volatility Weekly Recap

The figure below shows the term structures for the VIX futures (in colour) and the spot VIX (in grey).

Stocks pulled back from record highs as rising Treasury yields, higher oil prices, and renewed US-Iran tensions weighed on sentiment. The 30-year Treasury yield reached its highest level since 2007 before temporarily retreating after the Treasury announced expanded debt buybacks. Oil climbed, with Brent approaching $93, while gold rallied sharply following the buyback announcement.

Technology and semiconductor stocks were among the major laggards. Meanwhile, Bitcoin surged above $70,000 after the Treasury announcement and President Trump called for passage of the CLARITY Act, while Ethereum rallied more than 17% at one point.

On the volatility front, both the spot VIX and VIX futures rose slightly, but they remain in contango, and the roll yield is still positive. We observed that the short-term trend of the roll yield has turned upward. However, the spot/volatility correlation remains largely positive. In particular, the correlation between the S&P 500 and the implied volatilities of medium- and long-term fixed-strike options has remained positive (not shown).

Around the Quantosphere

  • Hedge Funds Suffer Worst AI-Driven Reversal in 20 Years as Investors Cut Crowded Tech Bets (tekedia)

  • Citadel Offloads 80% of Situational Awareness portfolio (hedgeweek)

  • A Niche Academic Team at Quant Hedge Fund AQR Is Researching Prediction Markets (efinancialcareers)

  • AI Has Lowered the Barrier to Quantitative Trading While Raising the Bar to Succeed (dailyexcelsior)

  • Morning Coffee: How the Citadel Traders’ Whisper Network Caught Leopold Aschenbrenner. Investment Banks Have AI Leaderboards Too (efinancialcareers)

  • A Canadian payment giant is being sold to U.S. private equity. Is your digital privacy at risk? (cbc)

  • Hedge Funds Are Piling Into Bonds, and That Could Be a Warning Sign (tipranks)

Disclaimer

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