The average balance in Fidelity Investments' IRA accounts grew by 53% to $81,100 in the five-year period to the end of the 2012 tax year.
Fidelity's annual analysis of its approximately 7 million IRA accounts, released Tuesday, also showed that total contributions increased by 7.5% from tax year 2008 to 2012, with the average contribution reaching $3,920 in the last tax year.
"Age-appropriate asset allocation strategies, market appreciation, and annual contributions all played a part in driving balances higher," Fidelity Investments vice president Ken Hevert said in a statement.
Fidelity said investors in their 60s continued to save the most in their traditional and Roth IRAs. For tax year 2012, they contributed on average $4,910 to Traditional IRAs and $4,840 to Roth IRAs.
As tax law changes were being debated on Capitol Hill in 2012, Roth IRA conversions increased by 12% year over year and by 52% year over year for the month of December.
Overall, Fidelity conducted more than 101,000 Roth IRA conversions with investors in 2012.
