At Fidelity, the average 401(k) balance hit $91,300 by the end of 2014. While that’s up just 2% from 2013, it’s a jump of more than 30% from 2011’s average balance of $69,100, Fidelity reported.

The increase was due in part to the stock market, which saw the S&P 500 climb by more than 10%– its third year of double-digit gains. But a spike in worker contributions also played a significant role.

Workers and their employers contributed an average of $9,670 in 2014, up 4% from the year before.