Reassessing VOO: Why Diversification Might Be Key in 2026

The Vanguard S&P 500 ETF (VOO) has long been a staple for investors seeking broad market exposure. Its low expense ratio and strong performance, particularly driven by the artificial intelligence (AI) rally in megacap tech stocks, have made it a popular choice. However, as 2026 unfolds, the market is showing signs of broadening beyond the tech sector, prompting a reevaluation of its role in investment portfolios. The S&P 500 index, which VOO tracks, has historically been heavily weighted toward technology stocks. Over the past decade, tech has consistently accounted for at least 20% of the index's performance, peaking at 36% in the previous year. Even after a recent correction, the sector still represents 32% of the index. This concentration has been a double-edged sword, delivering strong returns in recent years but now potentially dragging on performance as the market diversifies. For investors looking to mitigate this concentration risk, the Vanguard Total Stock Market ETF (VTI) offers a compelling alternative. VTI includes virtually every U.S. stock, with approximately 3,000 companies not part of the S&P 500. This broader exposure includes 75% in large-cap stocks and 25% in mid- and small-cap stocks. While it remains market cap-weighted, the inclusion of smaller companies helps diversify sector exposure and economic risk. The shift toward a more diversified portfolio is particularly relevant given the current market rotation. Small-cap stocks are benefiting from several catalysts, including improved economic conditions and investor sentiment. By adding VTI to a portfolio, investors can capture potential upside from mid- and small-cap stocks while maintaining exposure to large-cap leaders. This balanced approach may help reduce the impact of megacap concentration risk in the S&P 500. While VOO remains a strong ETF and can still serve as a core holding, the Vanguard Total Stock Market ETF is increasingly seen as a better option for both the short and long term. Its broader diversification provides a more balanced risk profile, aligning with the evolving market landscape in 2026.