刚刚，本轮美股牛市迎来“三周年纪念日”，在周五的“跳水”背景下

Core Insights - The current bull market in the U.S. stock market, which began in October 2022, has reached its three-year anniversary, with the S&P 500 index rising 83% and market capitalization increasing by approximately $28 trillion [1] - Despite a significant sell-off triggered by tariff threats from Trump, the S&P 500 index has still gained 13% over the past year, double the average gain for the third year of a bull market [1][2] - The S&P 500 index's price-to-earnings (P/E) ratio has reached 25, the highest level for the third year of a bull market, indicating a rapid increase in valuation levels [2][3] Valuation and Market Concentration - The current bull market is characterized by a rapid rise in valuation levels, with the S&P 500 index's rolling P/E ratio at 25, significantly higher than historical averages for the third year of bull markets [2] - There is a notable concentration of market performance among a few technology giants, with Nvidia rising nearly 1500% and Meta Platforms increasing over 450% in the past three years, while many other stocks have lagged behind [3] - The equal-weighted version of the S&P 500 index has underperformed the market-cap weighted version by 21 percentage points since October 2022, marking the largest lag since at least the 1990s [3] Investor Sentiment and Future Outlook - Despite existing risks, few professional investors predict an imminent bear market, with some suggesting that the Federal Reserve may intervene if conditions worsen [4] - There is a recommendation for investors to rebalance their portfolios, with a shift away from technology stocks towards undervalued sectors like healthcare [4][5] - Historical data suggests that bull markets typically last an average of 4.6 years, with the S&P 500 index returning approximately 157%, indicating potential for further gains in the current market [5]