Life expectancies for Americans are increasing, and 401(k) balances are woefully short to fund the average person’s retirement. That powerful one-two punch might force many people to rethink their retirement age. It’s not a happy thought for most folks, but nobody said reality is pretty.

“Seventy is the new 65,” said Charles Ellis, founder of the financial services consultancy Greenwich Associates and author of Falling Short: The Coming Retirement Crisis and What To Do About It. He spoke last month at the Morningstar ETF Conference in Chicago, where he noted the retirement age was set at 65 in 1935 when Social Security was enacted and life expectancies were shorter. Since people on average are living longer, he says the retirement age should go up as well to keep the retirement/working ratio constant.

“We need to relearn our retirement,” he said. “Otherwise, we’ll put ourselves in a predicament that’s hard to finance our way out of.”

Ellis’s presentation included some intriguing math: He said people’s monthly Social Security checks would be 76% more if they waited until age 70 to retire instead of collecting at age 62, the first year of eligibility. A person who receives $1,000 a month at age 62 would receive $1,760 at age 70. That increase comes from the delayed retirement credits recipients earn when they postpone benefits past their full retirement age.

He also said people who stay in the workforce until age 70—if they can—significantly increase their 401(k) balance. For many people, the period between the ages of 62 and 70 is often when they can save more because their children are likely grown and no longer need financial help. And most people are still relatively healthy at that age.

For example, if a person with a 401(k) balance of $110,000 (the median national amount) who makes $60,000 annually can contribute 12% each year between ages 62 and 70, and if the return on that 401(k) investment is 6%, the total gain during that time would be $150,000.

“The impact of $150,000 plus $110,000 equals $260,000,” Ellis said. “That makes a whale of a difference paid in retirement years. For that sort of deal, people are likely to work the extra years. Maybe they cannot work all eight years, but if they can stay as long as they can, they can increase their 401(k) balance.”

Since most Americans don’t have a pension and have to rely on their 401(k) plans—and their Individual Retirement Accounts and Social Security—to fund their retirement years, the underfunding of 401(k)s is a huge issue. Ellis noted the median balance of $110,000 for 401(k) plans isn’t enough to fund a retirement, especially as increasing numbers of people live into their 90s. According to the Society of Actuaries, a 65-year-old man has a 30% chance of living until 90 and a 65-year-old woman has a 41% chance.

To Ellis, rethinking a retirement that starts at age 70 rather than 65 can make a difference, and he offered ways to help people boost their retirement account balances.

For starters, employees need to update their skills and continue to learn new things to remain employable for as long as possible.  

Employers, for their part, should enroll employees automatically in 401(k) plans on their first day.