How much of your portfolio should be in stocks? It's one of investing's most important questions — and the standard answer is costing the average investor the equivalent of 2% of their lifetime consumption. Yale economists have finally built something better, and it fits in a spreadsheet.
Warren Buffett built his fortune through active investing, yet tells his family to put 90% in index funds. Why? His 44-year record reveals the answer: from 1981-2002, he achieved statistically significant alpha. But from 2003-2024, his performance became indistinguishable from luck. Academic analysis shows even his early success was systematic factor exposure plus cheap leverage, not stock-picking magic. If Buffett couldn't sustain alpha in mature markets, your fund manager w
Robin Powell
Oct 18, 202514 min read
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