Specifically, Akaka's "auto-escalation" bill, called the Save More Tomorrow Act, would increase the amount that automatically-enrolled employees contribute to the G Fund — which now is set at 3 percent of pay — by 1 percent each year for at least three years, according to TSP officials. This would mean automatically-enrolled employees would be contributing 6 percent within three years, and possibly more in the following years.

New military service members are not automatically enrolled in TSP and would not be affected by Akaka's bill.

The automatic increases would also push new Federal Employees Retirement System (FERS) employees to contribute the 5 percent necessary to receive the full matching contribution from their employing agency.

TSP in August 2010 began automatically enrolling newly-hired federal employees into the G Fund at a 3 percent contribution rate, unless they choose not to participate or change their investment options. Since then, 82,632 employees have been automatically enrolled in TSP.

The latest survey of TSP participants, which was released at Monday's meeting of the Federal Retirement Thrift Investment Board, found that 9 percent of FERS enrollees contribute less than 5 percent. Of those respondents who explained why they did not contribute the maximum, 18 percent said they did not know FERS employees receive matching contributions up to 5 percent, and 58 percent said they couldn't afford to put away that much.

Those statistics concerned TSP officials.

"They are basically leaving free money on the table," said Gregory Long, the board's executive director. "We still struggle with how to get this message out."

The bill has not yet been introduced, and does not have a number. The board has not taken a stance on Akaka's proposal.

The TSP survey found high levels of overall satisfaction with the plan. About 86 percent of respondents said they were satisfied or very satisfied with TSP — an increase from 2008, when satisfaction dipped to 81 percent. The board believes that decline from 2006 satisfaction levels of 85 percent was due to the financial crisis that collapsed the stock market.

The survey found TSP participants contribute an average of 11.5 percent of their paychecks toward their retirement savings. That is up from 10.3 percent in 2008, and is significantly higher than the 7.3 percent the average private-sector worker saves.

But some participants said they want more flexibility to take out loans and withdraw their money. For example, participants who take out hardship withdrawals today are not allowed to contribute to their TSP accounts for six months, and miss out on agency matching contributions during that period. Some survey respondents said they want to keep saving after making their hardship withdrawals.

Long said the board must consider those criticisms.

"Our younger group tends to be less satisfied than our older group," Long said. "Pretty soon, the older group will be retired and the younger group will be replacing them. We need to think about our design and our communication in the long term, because if we don't, we have the potential for declining satisfaction."

Long also said the board is starting to think about creating TSP apps for smart phones and tablets such as the iPad. But those apps will not be launched anytime soon, he said.