A Look at October's ETF Boom: What's Driving the Surge?

October saw a massive influx of money into US exchange-traded funds (ETFs), with a record-breaking $166 billion in net new assets. This surge was led by Vanguard, which had its best month ever, pulling in over $50 billion. The largest share of these inflows went into US stock ETFs, with large-blend ETFs capturing the most attention. Vanguard's S&P 500 ETF, VOO, was a standout performer, attracting nearly half of the flows into large-blend ETFs. VOO has been the most popular ETF of 2025, with $103 billion in flows year to date. Vanguard's success is not just limited to VOO; its Total Stock Market ETF, VTI, also played a significant role in propelling the company to the top spot for year-to-date flows. Despite the US stock market being more concentrated than it has been in decades, investors continue to pour money into technology-sector ETFs. October saw a record $8 billion in new assets flowing into these ETFs, which primarily invest in tech stocks like Nvidia, Microsoft, and Apple. However, it's important to note that these top holdings are not much different from those in the broader market, leading to potential overlap in investments.State Street's SPDR Portfolio S&P 500 ETF, SPYM, also had a notable month. After a name and ticker change, it broke its record for monthly flows. SPYM offers some advantages over its sibling ETF, SPY, including lower fees and the ability to reinvest dividends and lend securities. Interestingly, the declining price of bitcoin did not deter investors from pouring money into cryptocurrency ETFs. The largest spot bitcoin ETF, IBIT, saw solid inflows of $4 billion in October. Meanwhile, gold ETFs also performed well, with State Street's SPDR Gold Shares, GLD, making the top 10 list for ETF inflows in October. On the other hand, the trading-leveraged equity category saw the most outflows of any category, despite the number of trading-tool ETFs more than doubling over the first three quarters of 2025. This suggests that most investors are steering clear of these risky investments. In terms of performance, large-cap US stocks outperformed their mid- and small-cap peers. Emerging-market stocks also had a solid month, outperforming overseas developed markets.