If you're working a full-time 9-to-5 and contributing to a 401(k) plan, now might be a good time to check in and see what's going on with those automatic payroll deductions.

According to a new report from Fidelity Investments, many Americans may be surprised to find that they have achieved millionaire status.

Data from the pension plan company released on Tuesday finds that in the fourth quarter of 2023, the number of 401(k) accounts with more than $1 million grew 20% quarter-over-quarter and 41% year-over-year, with about 422,000 accounts falling into this range by the end of 2023.

Connected: What is a 401(k) and how does it work?

The average account balance for those who achieved 401(k) millionaire status by the end of 2023 was $1,551,300 in the fourth quarter.

“This past year ended on a high note for retirement savers,” said Sharon Brovelli, president of Workplace Investing at Fidelity Investments. CNN. “When it comes to issues such as market stability and economic events, 2023 gave us the highs of the highs and the lows of the lows but, encouragingly, many pension savers took the long view and stayed along the way, which is the kind of commitment that can lead to a secure financial future.”

The report also found that about 37.2% of employees increased their 401(k) contribution percentage in 2023, with 78% of employees participating in the 401(k) planning to contribute a percentage high enough to match the the full contribution of their employer.

Connected: 401(k)s are popular among Americans—and they pose a big risk

The report found that 27% of employees also actively increased their contributions to their 401(k) plans rather than relying on automatic increases or choosing to leave their contribution amounts as they are.

According to the data of Institute of Investment Companiestotal US retirement assets reached $35.7 trillion in the third quarter of 2023, with retirement assets accounting for 32% of all financial assets in US households as of September 2023.