What Warren Buffett's Investment Philosophy Reveals About the Right ETF Mix Today

The Simple Formula That Could Transform Your Portfolio

Warren Buffett has always championed simplicity in investing. His 2013 letter to shareholders made this crystal clear when he outlined what he’d suggest for his wife’s estate: a straightforward 90/10 split between an S&P 500 index fund and short-term government bonds. This wasn’t casual advice—it was a masterclass in portfolio construction that still resonates today.

The beauty of this approach lies in its elegance. Low fees. Long-term focus. No complexity. For the 90% equity portion, Buffett explicitly endorsed Vanguard’s offering, cementing his view that the Vanguard S&P 500 ETF (VOO) represents the gold standard for broad market exposure.

But what about the other 10%?

The Treasury Bill ETF That Fits Buffett’s Philosophy

Here’s where the Vanguard 0-3 Month Treasury Bill ETF (VBIL) enters the picture. This fund doesn’t make headlines, and that’s precisely why Buffett would suggest it as the perfect complement to an S&P 500-heavy portfolio.

The mechanics are straightforward: VBIL tracks U.S. Treasury bills with maturities of three months or less. Currently offering a 3.7% dividend yield with a razor-thin 0.07% expense ratio, it represents exactly what Buffett looks for in an investment vehicle—minimal costs paired with genuine returns.

Think about the macro context. Just a few years ago, Treasury bills were essentially dead weight in a portfolio, yielding nothing in the post-COVID environment. Today, that’s changed. A 3.7% yield—above current inflation rates—means your cash isn’t just sitting idle. It’s working for you.

Why This 90/10 Strategy Makes Sense Right Now

Berkshire Hathaway’s own playbook offers clues to Buffett’s thinking. The company maintains substantial cash reserves, ready to pounce when attractive investments appear or when markets offer better entry points. This isn’t cautious—it’s opportunistic.

By pairing VBIL with VOO, you’re essentially keeping dry powder available. If markets correct to more compelling valuations, you’ve got capital ready to deploy. Meanwhile, your Treasury bill allocation generates a steady return that covers inflation and then some.

The old Buffett wisdom about keeping “something in short-term government bonds” reflects a deeper understanding: not all money needs to chase maximum returns. Some of it should be positioned for optionality.

The Lesson in Two Funds

What emerges from Buffett’s decades of investing—and his explicit suggestions—is a model so clean it almost seems too simple. Two Vanguard ETFs. Two different purposes. One elegant solution.

The Vanguard S&P 500 ETF captures the upside of the world’s largest economy through its largest companies. The Vanguard 0-3 Month Treasury Bill ETF provides stability, yield, and the flexibility to act when opportunity knocks.

This combination doesn’t guarantee riches. But it does suggest a path forward for investors who value clarity over complexity—something Buffett has championed consistently throughout his career.