VOO’s Surge, SPY’s Retreat—and IBIT’s Relentless Rise

VOO has surpassed SPY as the largest S&P 500 ETF, widening the gap in assets under management and cementing its dominance thanks to its structural and cost advantages, while BlackRock’s IBIT continues to shatter ETF growth records by racing toward $100 billion in assets under management.

For three decades, the SPDR S&P 500 ETF, better known as SPY, reigned as the largest US equity ETF and benchmark for institutional liquidity. But rapid shifts in investor behavior have flipped the script in 2025. Investors have pulled a record $32.7 billion from SPY, accelerating its retreat behind the now-dominant Vanguard S&P 500 ETF, VOO. As of late 2025, VOO boasts an eye-popping $770 billion in assets under management (AUM), eclipsing SPY, which trails at $702 billion.

Why VOO Wins

VOO’s climb isn’t a mystery. Its expense ratio is just 0.03%, compared to SPY’s 0.09%—a fee difference that compounds meaningfully for long-term, buy-and-hold investors. In a landscape where retail investors control three-quarters of ETF assets, minimizing fees is paramount. SPY’s aging unit investment trust structure means it can’t reinvest dividends or lend securities, further eroding its competitiveness versus modern ETF structures like VOO.

The New ETF Power Base

The ETF market itself has exploded; there are now more ETFs listed in the US than individual stocks—a sign of the segment’s innovation and retail-driven energy. Institutions and professional traders may still chase SPY’s legendary liquidity, but the baton has passed to a new generation of investors who prize efficiency and cost over brand legacy.

A New Challenger: BlackRock’s IBIT

Meanwhile, a seismic new force is reshaping the ETF narrative: BlackRock’s IBIT Bitcoin ETF. IBIT’s growth makes VOO’s meteoric asset-gathering look slow by comparison. In less than two years since its 2024 launch, IBIT amassed over 800,000 bitcoin—valued at nearly $100 billion and now controlling 3.8% of global bitcoin supply. Its success signals a revolution in ETF investing and Wall Street’s acceptance of regulated digital assets.

Takeaway

With retail investors driving ETF growth, the US market is radically different than it was even a decade ago. VOO’s ascension blends fee discipline and structural advantage, while SPY’s withdrawal signals a changing of the guard. IBIT, breaking all inflow records, illustrates the vast appetite for new asset classes and rapid shifts in investor sentiment. The ETF landscape now offers more “flavors”—and if nearly identical performance can be bought for fewer pennies, cost-conscious investors know exactly where to go.

Quickly compare VOO, SPY, IBIT side by side with our ETF Compare Tool