According to Fidelity research, there were 769,000 401(k) millionaires at the end of June 2026, who as a group have been investing for an average of 25 years. While these investors have diverse backgrounds and circumstances, they share one investing habit nearly without exception: consistency.
Consistency in investing takes several forms, but many successful millionaire investors have relied on regularly purchasing index funds, such as the Vanguard S&P 500 ETF (VOO), which tracks the S&P 500 with a 0.03% expense ratio. According to the source, the S&P 500 compounded at approximately 10% annually from 1928 through 2025 when dividends were reinvested.
The power of this approach becomes clear through a concrete example. A 25-year-old investing $100 per week until age 65 would contribute $208,000 over their career. With consistent 10% annual returns, that investment would compound to approximately $2.4 million. Notably, this strategy requires minimal active attention—investors need only set up an automated purchase plan once at the outset.
However, consistent purchasing alone is insufficient. Successful investors also demonstrate what the source describes as “emotional consistency.” The S&P 500 experiences bear phases, bull phases, crashes, and volatile trading periods. Many investors feel tempted to pause contributions during market downturns or crashes—precisely when prices are lower and new purchases would be most advantageous. The source notes that maintaining a consistent long-term view and continuing weekly investments regardless of market conditions is the correct approach, even when fear makes pausing contributions seem appealing.
Consistency extends beyond index funds. The source indicates that millionaire investors often purchase certain high-performing blue chip stocks on a regular basis over time. Costco Wholesale and Apple are cited as examples of durable businesses with large customer bases, high brand value, and consistent earnings growth across various economic environments. However, the source cautions that most individual stocks are poor targets for consistent purchasing, as they lack the ability to adapt to changing economic conditions.
Ultimately, according to the source, showing up regularly to invest—even with an imperfect schedule, modest capital, or imperfect asset selection—likely outperforms those who invest only when feeling confident or motivated by momentary enthusiasm. Setting an automated schedule, particularly through 401(k) contributions, and committing to the long run represents the core habit separating millionaire investors from others.
Key facts
- Fidelity found 769,000 401(k) millionaires at end of June 2026 who averaged 25 years of investing
- The S&P 500 compounded at roughly 10% annually from 1928 through 2025 with dividends reinvested
- A 25-year-old investing $100 weekly from their first job until age 65 could accumulate approximately $2.4 million
- Consistent investors maintain purchasing through market downturns rather than pausing due to fear
- The Vanguard S&P 500 ETF has a 0.03% expense ratio