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Over the last 25 years, investor activity in U.S. equity markets has undergone a dramatic transformation. Following more than a decade of structural decline, institutional and insider turnover across the S&P 500 appears to be reawakening. The first quarter of 2024 marked a modest yet meaningful uptick in rotation, reversing a long-running trend of investor inertia. While overall activity remains below historical peaks, recent movement hints at a changing posture among long-term holders.

Larger institutional investment managers who manage over $100 million in assets are required to file quarterly reports known as Form 13F filings with the SEC. These filings disclose their holdings of publicly traded securities, offering insight into the investment behavior of large institutions such as hedge funds, mutual funds, pension funds, and insurance companies.

Using 13F filings and insider transaction data, the accompanying chart captures turnover as a percentage of shares outstanding, averaged across current S&P 500 constituents. Several inflection points mark this 25-year trajectory:

Dot-Com Aftermath (2002)

In the wake of the tech bubble, institutional investors rapidly reshuffled positions. The collapse of overvalued internet stocks triggered a wave of portfolio de-risking, resulting in one of the sharpest turnover spikes after the year 2000.

Global Financial Crisis (2008–2009)

Turnover peaked at a historic high of 26.77% driven by fear-based rebalancing, margin calls, and liquidity stress. This period marked a structural inflection in institutional behavior, followed by a prolonged decline in activity.

Q1 2013 – Post-’Fiscal Cliff’ Rebalancing

Following the resolution of the U.S. “fiscal cliff”—a set of expiring tax cuts and scheduled government spending cuts that threatened to trigger a recession if left unaddressed—in late 2012, investors reentered equity markets with renewed confidence. Institutional portfolios rotated into cyclical sectors and captured profits, leading to a sharp spike in turnover.

COVID-19 Pandemic (2020)

The early 2020 shock briefly reignited turnover as volatility forced tactical repositioning. However, this activity quickly subsided, and long-term investor engagement remained muted despite continued macro uncertainty.

Record Low Amid Retail Surge (2021)

As retail investors took center stage during the meme stock era—a period defined by the explosive rise of heavily shorted stocks like GameStop and AMC driven by online communities—institutional turnover fell to a record low of 11.96%. Passive flows and intense retail engagement likely displaced traditional portfolio rotation.

Q1 2024 – Active Management Reawakens

After years of subdued movement, Q1 2024 reflected early signs of institutional reengagement. Active managers began reasserting themselves amid fading retail momentum, a more stable rate environment, and evolving macro narratives. Insider participation also ticked up, suggesting rising conviction among corporate executives.

Q1 2025 – A Subtle Inflection

The most recent reading in Q1 2025 shows turnover climbing to 15.2%, extending the upward shift seen in 2024. While still modest in absolute terms, the movement suggests a possible turning point in long-dormant active investor behavior.

Post-2010 Decline in Turnover: The Rise of Passive Titans

While market shocks have triggered short-term turnover spikes, the dominant structural trend since 2010 has been a sustained decline in investor turnover—and the asset management landscape offers a compelling explanation.

Over the last 15 years, the concentration of equity ownership among the top 10 asset managers has grown substantially. Their total equity assets under management (AUM) ballooned from under $3 trillion in 2010 to over $19 trillion in early 2025. This growth correlates with the meteoric rise of passive investing, largely driven by index-tracking giants like BlackRock, Vanguard, and State Street.

Notably, this shift also displaced some prior incumbents from the top 10 list, including Barclays Global Investors, AXA Group, Allianz Group, and Deutsche Bank. UBS Group, which once topped the list in 2006, has also since fallen out of the top ranks.

Unlike active managers who frequently rotate holdings, passive funds maintain static positions, adjusting only for index changes or investor flows. As passive vehicles amassed trillions in equity exposure, they structurally reduced aggregate turnover across the S&P 500—even as market capitalization soared.

Key Observations

Turnover Suppression Effect: As passive (investors base) AUM rose, institutional turnover steadily declined, even during volatile macro periods.

Ownership Concentration: A small set of asset managers now hold large swaths of public float, dampening trading activity.

Market Structure Impact: Passive capital has created persistent, low-turnover ownership, reducing responsiveness to fundamentals in favor of index-level flows.

More Filers, Less Activity: A Participation Paradox

Another paradox emerges when considering the trajectory of institutional participation. Since the end of 1999, the number of 13F filers has more than quadrupled—from 1,943 to approximately 8,862 13F filers as of Q1 2025. On its surface, this suggests a democratization of equity ownership, with more firms reporting holdings in public companies. However, this expansion in breadth has not translated into greater turnover. In fact, aggregate S&P 500 turnover has declined sharply over this period.

Breakdowns by filer type reveal that this growth has been driven by specific segments. Investment advisers, private wealth managers, and hedge fund managers represent the only categories that have each surpassed 1,000 13F filers in recent years.

• As of the end of the 1st quarter of 2025, there were approximately 4,958 investment advisers, 1,445 wealth managers, and 1,289 hedge fund managers registered as 13F filers.
• Other segments—including insurance, pensions, banks, and family offices—grew modestly but
  remain small contributors.

The growth of these leading categories speaks to their magnitude in the institutional ecosystem. Together, they account for the vast majority of the observed expansion in the 13F universe.

However, the disconnect between filer growth and declining turnover underscores a structural reality: despite broader participation, ownership and influence have become increasingly concentrated in the hands of a few dominant passive managers. The rise of smaller, lower-activity filers—many of whom operate passive or low-churn strategies—has contributed to a dilution of average turnover without increasing meaningful trading activity.

Observations

More Filers, Same Power Players: While more firms are reporting under 13F, actual market influence remains heavily concentrated in a small number of dominant institutions.

Passive Growth, Minimal Movement: Many of the new entrants represent passive or low-turnover strategies, contributing to the filer count but not significantly impacting trading volumes.

Few Firms Drive the Market: A handful of top-tier asset managers control the majority of assets and trading outcomes, while most 13F filers operate with limited market impact.

Implications Going Forward

Though not yet a wholesale reversal, recent upticks in turnover signal a potential return to portfolio-level decision-making among active shareholders. For public companies, this evolving environment underscores the importance of:

• Reassessing investor targeting strategies
• Preparing for greater variability in ownership
• Monitoring emerging themes that drive rotation

Since 2010, equity markets have been shaped by the rise of passive investing and waves of retail activity, leaving institutional turnover at historic lows. Now, with signs of active managers reengaging, a shift may be underway. Even a modest return to active decision-making could mark the start of a post-passive era. Investor relations teams should prepare for a more dynamic ownership landscape—one increasingly driven by fundamentals—and act accordingly.