Core Insights - The S&P 500 is experiencing record concentration among a small number of stocks, which raises concerns about the sustainability of high valuations [1] - This concentration suggests a potential need for investors to diversify their portfolios to mitigate risks associated with over-reliance on a few stocks [1] Investment Implications - High valuations in the S&P 500 indicate that the market may be overvalued, prompting a reassessment of investment strategies [1] - Broadening investment portfolios could provide better risk-adjusted returns in the current market environment [1]