During the weekend of the Berkshire Hathaway annual meeting, Omaha is particularly quiet. It’s not exactly silence. It sounds more like a quiet conversation about index funds among sensible people in sensible shoes who are waiting in line for cinnamon rolls outside the convention center while holding coffee. It’s America’s least thrilling investment group. which is, in a sense, the whole point.
That culture is home to Warren Buffett’s 90/10 rule. In his 2013 shareholder letter, he gave a clear explanation of what he had told the trustee of his wife’s estate to do after his death, almost in passing. He advised investing 90% of the money in an extremely inexpensive S&P 500 index fund and 10% in short-term government bonds. That was all. Not a single exotic structure. There are no tax havens. No covert hedge.
| Topic Snapshot | Details |
|---|---|
| Strategy Name | The 90/10 Rule |
| First Proposed | Warren Buffett’s 2013 shareholder letter to Berkshire Hathaway investors |
| Allocation | 90% in a low-cost S&P 500 index fund, 10% in short-term government bonds |
| Recommended Fund Family | Vanguard, per Buffett’s own suggestion |
| Historical S&P 500 Return | Roughly 10% annual average before inflation, over nearly a century |
| Sample Calculation | If S&P 500 returns 10% and T-bills return 4%, the blended return is about 9.4% |
| Originally Intended For | The cash bequest left to Buffett’s wife in his will |
| Critics’ Main Concern | Heavy equity exposure for retirees, sequence-of-returns risk |
| Closest Academic Test | Javier Estrada at IESE Business School, who simulated retirement scenarios |
| Underlying Bet | The long-term durability of the American economy |
| Article Length | 500–600 words |
It generated a surprising amount of controversy for something so straightforward. Advice that doesn’t involve Wall Street usually makes Wall Street wince. The most successful investor of the modern era essentially stated in writing that most people would do better ignoring everything. Financial advisors spent entire careers explaining why a 60/40 portfolio was the prudent default.
The rule might sound too good. However, the math is nearly embarrassingly clean. For almost a century, the S&P 500 has averaged about 10% annually prior to inflation. A 90/10 portfolio divides the difference between a thin shock absorber and maximum upside. The blended return is approximately 9.4% if Treasury bills return 4% and stocks return 10% in a given year. Fees are nearly completely eliminated by index funds. Year after year, year after year, compounding takes care of the rest.
Buffett has more faith in indexing than those who manage money for a living, and there’s a reason for this. After deducting their fees, the majority of active managers consistently fall short of the S&P 500. For decades, he has expressed this opinion, sometimes with a sly smile and other times with the tolerance of someone who is sick of saying the same thing over and over. The 90/10 rule is a subtle critique of an entire industry as well as a portfolio design.
However, Buffett himself doesn’t truly follow the rule, and it isn’t ideal for everyone. Berkshire has a notoriously massive cash pile and has been a net seller of stocks for years. A 90% equity weighting can be harsh for someone who has already retired, and a sharp decline in withdrawals in the first or second year can permanently damage a portfolio, as critics rightly point out. The 90/10 rule doesn’t really mitigate sequence-of-returns risk.
Observing this debate over the years has given me the impression that people continue to want Buffett’s rule to be more intricate than it actually is. They’re looking for exceptions. adjustments. updates for higher rates, the AI era, and whatever the current panic may be. After making one minor change—withdrawing from stocks when they were rising and bonds when they were falling—IESE researcher Javier Estrada, who actually ran the numbers, came to the conclusion that the strategy worked perfectly.
The 90/10 rule is probably sufficient for the majority of people in their thirties, forties, and even early fifties who have a long horizon and a tolerance for occasionally witnessing the market scream. Not glitzy. Not very smart. Just enough.
