Data from the NYSE and FINRA reveal that the scale of margin debt in the U.S. has surged to approximately 4.5% of the Gross Domestic Product (GDP), setting a historical record and surpassing previous peaks during the 2000 dot-com bubble, the 2008 financial crisis, and the market highs of 2021. Margin debt refers to the liabilities incurred by investors when borrowing money to purchase stocks. High leverage can amplify investment returns in a bull market, but it significantly increases the risk of forced selling during downturns. Although this indicator cannot precisely predict market turning points, it reflects that the current level of investor leverage is at an unprecedented high relative to the size of the economy in modern history.