The market concentration within the S&P 500 has reached levels not seen in six decades, with the top 10 companies now accounting for approximately 37% to 40% of the index's total market capitalization. This surpasses the peak concentration during the 2000 Dot-Com Bubble by about 10 percentage points. Meanwhile, the next 40 largest stocks hold only around 22.8% of the market share, the lowest on record. Despite the high market cap concentration, the top 10 companies' earnings share stands at 30%. Analysts suggest that in such an environment, equal-weighted investment options like the RSP ETF may outperform capitalization-weighted funds such as SPY over the next five years, as historically when the top 10 market cap exceeds 23%, the broader market tends to benefit.