Worried About Record Stock Market Concentration? Us, Too

Core Insights - The concentration of the stock market is at an all-time high, with the top 10 US companies having a market capitalization of nearly $24.4 trillion as of October 23, representing over 43% of the S&P 500 [1][2] - Nvidia alone accounts for nearly 8% of the S&P 500, equating to the total value of all 2,000 small-cap companies in the Russell 2000 index [2] - The concentration of the top 10 companies in the S&P 500 increased by 8.2 percentage points from 34.8% to over 43% in just over 15 months [2] Market Dynamics - Large-cap growth stocks, particularly in the tech sector, have significantly outperformed small-cap value stocks over the past decade [2] - Historical analysis suggests that increased market concentration is typically a sign of a bull market rather than a precursor to a bear market [3] - Despite common perceptions, elevated concentration has often been followed by market rallies rather than declines [3] Investment Strategies - One strategy to mitigate concentration risk is to invest in an equal-weight S&P 500 index fund, which would reduce the influence of the top companies [3] - However, this strategy has underperformed compared to cap-weighted funds, with the Invesco S&P 500 Equal Weight ETF gaining only 7.6% and 14.5% over one and three years, respectively, compared to the Vanguard S&P 500's gains of 16.0% and 23.1% [3]