The number of workers who participated in workplace retirement plans dropped slightly in 2012 to 39.4 percent, or 61.6 million Americans. But among full-time, full-year wage and salary workers, 53.5 percent participated.

According to the Employee Benefit Research Institute, the individuals who were least likely to participate in an employer-based plan were non-white, young, female, never married, those having a lower educational attainment, lower earnings, poor health, no health insurance, those working part-time or those working in farming, fisheries or forestry occupations.

Those working for smaller firms, private-sector firms or firms in the "other" services category were also less likely to participate in a plan than their comparison groups.