A major divergence is happening in exchange-traded funds (ETFs) tracking the blue-chip S&P 500 Index. The Vanguard S&P 500 ETF (NYSE:VOO) has continued to achieve record inflows as the popular SPDR S&P 500 ETF (NYSE:SPY) shed billions of dollars in assets. VOO ETF Inflows Are Soaring This Year Data compiled by ETF.com shows that the VOO ETF has had over $59 billion in inflows this year, bringing its net assets to over $927 billion. This makes it the biggest ETF in the United States and one of the fastest-growing ones. VOO was started in 2010 and will be the first fund to hit a $1 trillion AUM milestone. In contrast, SPY, which is one of the most common ETFs, has continued to shed assets this year. It has had almost $9 billion in outflows, giving it over $797 billion in assets. Data shows that it has shed $20 billion in assets since January last year, while VOO has added $196 billion in the same period. VOO ETF inflows since January 1, 2025 | Source: ETF SPY Has A Higher Expense Ratio Than VOO The ongoing divergence is likely because of the fee differential between the VOO and SPY. VOO charges an expense ratio of just 0.03%, while SPY has a fee of 0.09%. A $1 million investment in these two funds costs $300 and $945 annually. The $645 difference is notable given that both funds track the same index, and that gap compounds meaningfully over time. This fee differential explains why Morningstar (NYSE:MORN) has given VOO a gold star rating compared to SPY's silver. Still, it is not all bad for State Street, which runs the SPY ETF. For one, the company launched the SPDR Portfolio S&P 500 ETF (NYSE:SPYM) in 2005. It has an expense ratio of 0.02% and has accumulated over $148 billion in assets under management. Its inflows have jumped by over $45 billion since January last year. Read Also: Are Dividend ETFs Like SCHD, DGRO, VYM Appealing As Bond Yields Jump? Investors have become increasingly sensitive to fees charged by companies like Invesco, BlackRock, and Vanguard. For example, the Invesco NASDAQ 100 ETF (NASDAQ:QQQM), which has an expense ratio of 0.15%, has had over $31 billion in inflows since January last year. Invesco QQQ Trust Series 1 (NASDAQ:QQQ), which costs 0.25% in assets, has added $24 billion in inflows in the same period. Investors have increasingly turned to ETFs this year, with a report showing that they have added $725 billion. This growth is being driven by the ongoing stock market surge, with the top indices like S&P 500 and the Nasdaq 100 soaring to a record high. Read Also: Pi Network Price Eyes All-Time Low Despite Pivoting to AI, Smart Contracts Image: Shutterstock