The number of investment choices is critical to employees’ confidence regarding the adequacy of retirement savings.

One-third of Americans who participate in an employer-sponsored retirement plan say they are not familiar with the plan’s investment options, according to a new TIAA-CREF survey.

The research shows a pronounced difference between male and female respondents, with 37 percent of women stating they are not familiar compared to 29 percent of men. Generational differences also are apparent, with 43 percent of Gen Y respondents stating they are not familiar with their plan options.

The survey was conducted by an independent research firm and polled a random sample of more than 1,000 adults nationwide on their retirement plans.

The report reveals that 39 percent of people who are familiar with their investment options save more than 10 percent of their annual income for retirement. This is nearly double the percentage (21 percent) of people who are not familiar with their options.

Twenty-eight percent of survey respondents say they do not understand all of their choices for how to invest their money in their retirement plan. More than one-third (36 percent) believe they have either too many or too few investment choices.

“The number of investment choices in a retirement plan makes a critical difference in employees’ confidence regarding the adequacy of their retirement savings,” the report states. “Those who feel they have the wrong amount of investment choices are more likely to be concerned about running out of money in retirement.”

Nearly two-thirds (65 percent) of those who think they have too many investment choices are very or somewhat concerned about running out of money in retirement, as are 55 percent of those who don’t think they have enough choices. By contrast, the report adds, 40 percent of respondents who believe they have the right number of investment choices are “not at all concerned” about running out of money in retirement.

The survey observes also that 81 percent of respondents trust financial information offered by their employer, a greater percentage than those who trust financial information offered by a traditional financial institution, such as a bank or retirement plan provider (69 percent), or their family (63 percent).