It's commonly cited that 50 percent of American workers have access to employer-sponsored retirement plans, but the share of population that will have accrued such retirement benefits will be far greater, says the Investment Company Institute.

The 50 percent number applies to workers age 21 to 64 and includes young workers who may not care if they work for an employer who provides pension benefits, says ICI. Instead 21- to 30-year-olds are more focused on saving for a house or paying for education, ICI maintains.

In contrast, 60 percent of workers 30- to 64-years-old have access to company-sponsored retirement plans, says an ICI study, Who Gets Retirement Plans and Why, 2011.

The percentage jumps to 69 percent for employees 30 to 45 who earn at least $45,000 or more and those 45 and older who make at least $25,750, ICI says. The 45-and-older group is more focused on retirement and 93 percent participate in their employer's retirement plan, ICI says.

"Policy discussions surrounding retirement often focus on the headline statistic that about 50 percent of America's workers are covered by workplace retirement plans," says Peter Brady, ICI senior economist and a co-author of the study. "This study shows that older, full-time workers are much more likely to have access to an employer-sponsored retirement plan."

"Looking at the percentage of all workers who have coverage today understates the share of the population who will reach retirement having accrued employer-provided retirement benefits," he says. "Many workers who do not have access to an employer plan today will have access prior to retirement."

At the same time, retirement plan coverage for the overall workforce, including younger workers, averaged 54 percent between 1979 and 2011 and was 50 percent in 2011.

-Karen DeMasters