Core Insights - The U.S. stock market is increasingly dominated by large tech companies, with the S&P 500 now representing 84% of total U.S. market capitalization, up from 75-80% in previous years [3] - Nvidia and Microsoft, the two most valuable U.S. companies, have a combined market cap equivalent to approximately 3,000 companies outside the S&P 500 with market caps over $250 million [4] - Vanguard's Total Stock Market ETF is the largest publicly traded fund globally, with over $2 trillion in net assets, surpassing the Vanguard S&P 500 ETF [5] Fund Comparisons - Both the Vanguard S&P 500 ETF and the Vanguard Total Stock Market ETF have an expense ratio of 0.03%, making them the lowest-cost options available [8] - The Total Stock Market ETF holds 3,529 stocks compared to 504 in the S&P 500 ETF, providing greater diversification [9] - The S&P 500 ETF is suitable for investors seeking simplicity, while the Total Stock Market ETF may be better for those wanting exposure to smaller stocks outside the S&P 500 [10]