The median increase in the account balance for the group of Roth IRA owners in the study was 16.5 percent from 2010 to 2012, compared with 7.9 percent for owners of traditional IRAs, according to the Employee Benefits Retirement Institute (EBRI).

Roth IRA balances also grew faster than traditional IRA balances for each age group studied and for each gender, EBRI said.

Roth IRAs, named after Sen. William Roth who sponsored the legislation creating the accounts under the Taxpayer Relief Act of 1997, are more flexible with regard to penalties and taxes compared with regular IRAs.

The EBRI analysis was derived from a consistent set of IRA owners.

Craig Copeland, senior research associate at EBRI, said the “longitudinal sample” used in the study allows analysts to assess the IRA investing behavior of the same investors over the time period.

One of the reasons for faster growth rates in Roth IRAs compared to traditional IRAs was due to new contributions making up a larger portion of the Roth IRA balances due to smaller average balances of Roth IRAs, EBRI said.

In a Roth IRA, withdrawals are tax free on savings during retirement, and access to annual contributions before retirement is penalty free. In addition, investors avoid required minimum distributions after age 70 ½, and account holders may contribute after age 70 ½.

Copeland said that about 25 percent of Roth IRA owners contributed in any one year compared with 35 percent who contributed at some point over the three-year period.

Other findings of the EBRI IRA study revealed that the overall average IRA account balance in 2012 was $81,660, while the average IRA individual balance — all accounts from the same person combined — was $105,001.

Rollovers outweighed new contributions in dollar terms, and 10 times as much was added to IRAs through rollovers compared to contributions, the study found.

The average individual IRA balance increased from $11,009 for owners ages 25 to 29, to $192,961 for owners ages 70 or older, according to the study.

Men had higher individual average and medial balances that women: $139,467 and $36,949 for men, respectively, compared with $81,700 and $25,969 for women, the study found.