In an era in which “get rich quick” schemes involving cryptocurrency and day trading dominate social media feeds, a quiet army of everyday workers is building substantial wealth using a strategy that is remarkably boring—and effective. According to financial expert and bestselling author David Bach, recent data reveals a specific asset allocation formula shared by hundreds of thousands of retirement account millionaires: the 70/30 rule.

Bach, author of The Automatic Millionaire, recently appeared on The Diary of a CEO podcast to discuss the habits of the wealthy. He highlighted recent statistics from Fidelity Investments showing there are now approximately 654,000 “401(k) millionaires” in the United States, meaning their fortune is entirely derived from their retirement account, usually conservatively invested. The Wall Street Journal calls these thrifty and wealthy investors “moderate millionaires,” and they share a strong resemblance to UBS’s “everyday millionaires.”

When analyzing how these ordinary employees amassed such fortunes, a clear pattern emerged. They didn’t trade meme stocks or time the market. Instead, they saved consistently and adhered to a specific investment mix: roughly 70% in stocks for growth and 30% in bonds for stability.