But Obama’s proposal rests on a pair of uncertain assumptions: that employers would be willing to offer the accounts and that financially stretched low-income workers would agree to participate in them.

In contrast to 401(k) plans, companies would not offer matching contributions, typically the biggest inducement for workers to get involved.

“I don’t expect it to accomplish any increase in retirement savings,” said Teresa Ghilarducci, an expert in retirement issues at the New School in New York. …

Money would be invested in a government bond fund that’s been offered to federal employees for years. Principal would be protected so that workers would never lose money.

But they probably wouldn’t earn significant returns. In 2012, the fund had a 1.47% return. The 10-year average annual return was 3.61%.