Vanguard ETFs Offer Investors a Way Out of S&P 500 Concentration

For decades, the S&P 500 has been the default choice for U.S. investors seeking broad exposure to the stock market. But the index's composition has shifted dramatically, with technology stocks now making up nearly 40% of its weight and the top 10 companies controlling more than 40% of its total market capitalization as of June 2026. This level of concentration means that what was once considered a diversified core holding now behaves more like a focused bet on a handful of mega-cap tech names.

Recent volatility has exposed the risks of this concentration. On June 5, the S&P 500 dropped 2.6% in a single session, a move that hit investors who expected the index to buffer against sharp swings. According to the American Association of Individual Investors, eight of the S&P 500's 10 largest companies operate in the technology or communication services sectors, making the index especially vulnerable to sector-specific downturns or disappointing earnings from a few giants.

Concentration Risk and the Search for Diversification

Analysts at VanEck and Royce Investment Partners have highlighted the growing imbalance in the S&P 500, warning that a passive allocation to the index now amounts to an unintended overweight in technology. The share of the index held by its top 10 companies has more than doubled since 2016, when it stood at about 18%. This shift has prompted some investors to look beyond the S&P 500 for true diversification, especially as small-cap and international stocks remain underrepresented in the benchmark.

One approach is to rotate some gains into international and emerging market equities, which can diversify both by geography and sector. Others are focusing on areas like healthcare and infrastructure, which may be less exposed to the risks of artificial intelligence disruption or could benefit from AI-driven productivity gains.

Small-Cap ETFs: A Different Profile

Small-cap stocks have lagged large caps for much of the past decade, but that trend has started to reverse. The Russell 2000, a widely followed small-cap index, gained 43.1% in the year ending May 31, 2026, outpacing the large-cap Russell 1000's 28.8% return, according to Franklin Templeton. The Vanguard S&P Small-Cap 600 ETF (VIOO) offers targeted exposure to this segment, with a key distinction: it tracks an index that requires companies to be profitable before inclusion, screening out unprofitable firms that can drag down returns in other small-cap benchmarks.

VIOO holds over 600 stocks, with its top 10 positions accounting for just 5% of assets-a stark contrast to the S&P 500's concentration. The fund's price-to-earnings ratio was 16.8, and its earnings growth rate stood at 12.5% in the first quarter of 2026, based on Vanguard's latest fact sheet. Analysts expect earnings-per-share growth for the S&P SmallCap 600 to reach 22.9% in 2026, compared to 16.4% for the S&P 500, according to CFRA research.

International Stocks: Lower Valuations, Higher Yields

Developed international markets are trading at a significant discount to the S&P 500, with a forward price-to-earnings ratio of about 16 versus 22 for the U.S. benchmark, according to VanEck. In 2025, international stocks outperformed U.S. equities by roughly 14 percentage points, helped by a weaker dollar. Goldman Sachs Research projects that the dollar will continue to weaken through 2026, potentially providing a tailwind for U.S. investors holding unhedged international funds.

The Vanguard Total International Stock ETF (VXUS) covers companies across Europe, Japan, and emerging markets, with an annual expense ratio of 0.05%. As of June 30, 2026, VXUS paid a dividend yield of 2.33%, exceeding the S&P 500's payout. For investors seeking to fill the mid-cap gap left by the S&P 500, the Vanguard Total Stock Market ETF (VTI) holds more than 3,500 U.S. stocks, including mid- and small-cap names that the S&P 500 omits.

Broader Strategies for a Changing Market

VTI's portfolio overlaps with the S&P 500 by about 82% by weight, but its inclusion of smaller companies adds diversification that the benchmark lacks. During several periods in 2026, smaller stocks have outperformed large caps, underscoring the value of broader exposure. Both VanEck and Royce analysts argue that shifting some allocation into small-cap and international ETFs can help address the concentration risk flagged by the AAII.

For retirees and those managing large IRAs, strategies to sidestep new tax limits and maintain diversification are increasingly relevant. As discussed in this analysis of Vanguard's IRA strategies, understanding the structure and holdings of your core funds is essential to managing both risk and tax exposure in a changing market environment.

According to S&P Dow Jones Indices, the S&P 500's technology sector weighting reached 39.7% in June 2026, the highest in over 20 years. The index's top 10 holdings-dominated by companies like Apple, Microsoft, and Nvidia-now account for 41.5% of total market cap. By comparison, the S&P SmallCap 600's top 10 holdings represent just 5% of its assets, and the Vanguard Total International Stock ETF's largest positions make up less than 10% of the fund. These figures highlight the growing concentration risk in the S&P 500 and the potential benefits of diversifying across market segments and geographies.

Index concentration risk arises when a small number of companies dominate a benchmark, making its performance highly sensitive to the fortunes of those firms. In a cap-weighted index like the S&P 500, larger companies exert more influence on returns, which can distort the diversification investors expect. While this structure can boost returns during periods of strong performance by mega-cap stocks, it also increases vulnerability to sector-specific shocks or regulatory changes. Investors should regularly review the composition of their core holdings and consider supplementing with funds that target small-cap, mid-cap, or international stocks to achieve a more balanced portfolio.