GAO Report pegs IRA account balances at $5.2 trillion

"An individual who made the maximum contributions every year since 1975 to a traditional IRA could have accumulated about $303,420 achieving investment returns equal to the average annual Social Security rates," the report adds.

To accumulate an IRA balance of $1 million, an individual who made the maximum allowable IRA contributions ($99,500) between 1975 and 2011 would have needed to achieve a dollar-weighted rate of return of 11.6 percent, the report shows. To secure a balance of $5 million, the rate of return would have needed to be 18 percent.

"It would take double-digital rates of return — well in excess of the S&P 500 return over the period — to achieve a balance of $1 million or more, assuming an individual only made IRA contributions," the report states.

With Congress expected to take up a debate on tax reform in 2015, the merits of maintaining the current tax-favored treatment of IRAs — pre-tax contributions grow tax-deferred — will hinge in part on whether lawmakers decide the tax benefits accruing to retirement savers outweigh the lost tax revenue. In 2014, tax-preferred tax for IRAs will result in the federal government forgoing $17.5 billion in net income tax revenue, according to estimates by the U.S. Department of the Treasury.