In a thought-provoking memo, Howard Marks discusses the current state of market bubbles and their implications for investors. The first decade of the 21st century provided investors with two notable bubbles, leading to both opportunities and losses. Marks notes that as of the end of November, U.S. equities constituted over 70 percent of the MSCI World Index, a striking figure that hasn’t been seen since 1970. His analysis invites investors to reconsider their strategies and be cautious about the current market dynamics. Understanding these trends becomes crucial to navigating future investment opportunities.