Investment Letter September 2026 

In this ninth investment letter of 2026, I review the portfolio’s performance and key developments from the past month, September 2026.

In this edition:

• Transactions: An overview of the transactions I made in September.
• Portfolio: An overview of my portfolio as of September 30, 2026.
• The Wisdom of Buffett & Munger: 3 insightful comments from Warren Buffett and Charlie Munger at the Berkshire Hathaway shareholder meetings of 1994-1997.
• Portfolio Management: The 3 core themes for building a sound investment strategy: behavior, concentration vs. diversification, and quality vs. valuation.
• Howard Marks: My takeaways from the memo Shall We Repeal the Laws of Economics – Part III, published on September 22.
• Mauboussin & Callahan: My takeaways from the paper To Free or Not to Free (Cash Flow), published on September 17.

Content: 

• Author: Eelze Pieters
• Language: English
• Format: PDF
• Number of pages: 28 (A4) 
• Publication date: October 20, 2026
• With illustrations

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