Just as travelers will have a hard time reaching a destination if they don’t know where they’re going, savers will have a hard time preparing for retirement if they don’t know how long retirement will last, according to a recent study.

Longevity literacy, or ability to understand just how long the average retirement will be, and what that means for them, strongly correlates to retirement readiness, said an analysis from TIAA and George Washington University.

Adults who display high levels of longevity literacy are more likely than those with lower levels of literacy to not only know how much they need for retirement, but to regularly save for retirement and to report feeling confident in their retirement preparations, according to analysis of a survey of more than 3,500 adults. Similarly, high-literacy adults in retirement were more likely to report living a lifestyle that met or exceeded their expectations than their lower-literacy peers, and were more confident that their savings would last the duration of their retirement.

The problem, according to the researchers, is that too few U.S. adults are displaying longevity literacy. Just 35% of the respondents in the survey could accurately estimate the average lifespan of a retiree from age 65.

“Longevity literacy is particularly important since retirement income security inherently involves planning, saving and preparing for a period that is uncertain in length,” said Surya Kolluri, head of the TIAA Institute, in released comments. “Our research clearly demonstrates a lack of longevity literacy among the vast majority of U.S. adults. Improving this can promote better retirement security and mitigate longevity risk.” 

Respondents in the survey were much more likely to underestimate potential longevity than they were to overestimate it. Men were significantly more likely to underestimate longevity at retirement age than women.

Longevity literacy was even lower when the respondents were asked about survivorship to very old age, 90, or relatively early death, 70. Just 12% of respondents could correctly identify both that men have a 30% chance and women have a 40% chance of living past 90, while men have a 5% to 10% and women have less than a 5% chance of dying at or before age 70. These 12% were found to have a “strong longevity literacy,” while another 31% of the survey who had underestimated retirement lifespans were deemed to have had a “weak longevity literacy.”

The discrepancies between the “strong” group and the “weak” group ahead of retirement were stark. Half of the strong respondents determined how much they need to save for retirement, compared to 32% of those with weak longevity literacy. Nearly three-quarters of the strong respondents, 72%, were saving for retirement, versus 58% of the weak group. Significantly more of the strong respondents, 69%, were confident about having enough money to live comfortably throughout retirement, compared to 53% of those with weak literacy.

The divergence continues after retirement, according to the survey. More than three-quarters of the strong respondents, 77%, said their current lifestyle meets or exceeds their pre-retirement expectations, compared to 62% of those with weak literacy. Also, 82% of strong respondents said they are confident they have enough money to live comfortably throughout their retirement, compared to 69% of those with weak literacy.