Former Vice President Joe Biden, President Donald Trump, and Sen. Bernie Sanders are actually at the same place in their lives as most other presidents, the writer says. (The Minnesota Star Tribune)

As the Super Tuesday dust settles, observers keep talking about the ages of Joe Biden and Bernie Sanders, who have amassed the most delegates, as though this should be a matter of serious concern.

I'd like to dissent, for two reasons. First and most obviously, we're suffering from recency bias. Before President Donald Trump, we had three consecutive two-term presidents who were relatively young: Bill Clinton, who was 46 on Election Day of 1992; George W. Bush, aged 54 in 2000; and Barack Obama, who was 47 in 2008. Before that, presidents tended to be older.

More to the point, when analysts tell us that Sanders or Biden, if elected in November, would be the oldest president in U.S. history, they're omitting relevant data. Age isn't an absolute. We live longer than we used to, and that's as true of presidential candidates as it is for anyone else. The more useful comparison is life expectancy adjusted for age at the time of election — in simple terms, how much longer the median person of the candidate's age would be expected to live.

For example, life expectancy for a person born today in the U.S. is 78.7 years. But a 65-year-old can expect to live about 18 more years, to age 83. We can call this second figure age-dependent life expectancy. If we're thinking about the age of a potential president, this is the number we should care about.

So what do the figures teach us over time? The statistics site eldo.co ran the numbers for us during the 2016 election campaign, when commentators also kept pointing out how old the candidates were. The analysis found that Donald Trump and Hillary Clinton were indeed significantly above the median age of nominees past, but also explained why focusing on age alone was deceptive: "Even though modern-day candidates are considerably older than they were a century ago, they are running for president at pretty much the same point in their lives as their counterparts 50 and 100 and 150 years ago."

The site pointed out that when age was considered relative to expected further years of life, the 2016 candidates were not unlike the nation's first president: "Hillary Clinton is at a pretty similar point her life (69.0, 80%) as George Washington when he first ran for president in 1788 (56.8, 78%). And Donald Trump is at a similar point in his life (70.4, 83%) as Washington when he won reelection in 1792 (60.7, 82%)."

The comparison with Washington is instructive, because he was old for his time. In 1793, Edward Wigglesworth of Harvard conducted the first study of mortality in the U.S., and found that in New England, white males died on average at age 36.5. Life expectancy at the time is estimated as the mid-40s. But here one must be cautious. Mortality rates at the time were heavily driven by infant deaths. According to much-cited research by the historian Richard D. Brown, the drafters of the Constitution largely fit the mortality patterns of other successful men of their era. Their average age in 1789 was 43; they died, on average, at age 65. For the population as a whole, those who attained the age of 40 in the late 18th century had an age-adjusted life expectancy of 25 more years. The Framers fit the model just about to the digit.

Ronald Reagan, when he won his second term, became the oldest president ever relative to life expectancy, at 88%. This year's leading Democratic candidates would indeed be older, but not by that much. On Election Day 2020, Bernie Sanders would just have turned 79, and Joe Biden would be just short of 78. For a 78-year-old male in the U.S., life expectancy is about 87.43, according to the Social Security Administration. For a 79-year-old male, the figure is 87.88. This means that Biden, if elected, would be at around 89.2% of his age-adjusted life expectancy; Sanders would be at around 89.9%. Either of them would beat Ronald Reagan's record of 88% — but just barely.

All of this is by way of saying that the age of the 2020 presidential candidates shouldn't be an important factor. Which is just as well: There are any number of more serious issues to talk about.