Several of the leading Democratic presidential candidates like Bernie Sanders and Joe Biden, as well as incumbent President Donald Trump, will be well into their 70s on Election Day in 2020.

Historically, that is at the upper edge of the age distribution for major party presidential candidates.

But rising life expectancies mean that old age isn't what it used to be.

Some of the likely contenders for the 2020 US presidential election are older than most historical candidates.

On Wednesday, Axios published an article noting the advanced age of several of the top Democratic candidates for the presidential race. It included a chart showing the age of each major party nominee going back to the 1900 election, including some of the older Democratic candidates who have announced or are likely to announce their intentions to run in 2020.

We have a similar chart below showing the Republican and Democratic nominees and their ages on Election Day, along with six leading Democratic candidates for the 2020 race and President Donald Trump, who will presumably be renominated by the Republican Party:

Presidential nominee ages have tended to rise over the last 120 years, particularly among Republican standard bearers. The 2016 election was notable, as both parties nominated older-than-average candidates, with Trump at 70 years old on Election Day, and Democratic nominee Hillary Clinton not far behind at 69. That made 2016 the first election since at least 1900 in which both major party candidates were over age 60.

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The 2020 race on the Democratic side is shaping up to include candidates of even more advanced age. As Axios noted, three of the leading candidates will be over the age of 70 by Election Day in 2020.

Senators Bernie Sanders and Elizabeth Warren, who have both officially announced that they are running for president, will be 79 and 71, respectively, on November 3, 2020. Former Vice President Joe Biden, who has not officially announced a run, but who has led several early polls of the race, will be 77 years old on Election Day.

Not all of the leading Democrats are septuagenarians, however. Senator Kamala Harris will be 56 years old on Election Day, Senator Kirsten Gillibrand will be 55, and Senator Cory Booker will be 51, to name three younger prominent candidates.

Read more: Here's everyone who has officially announced they are running for president in 2020

Perhaps it should not be surprising that older candidates are more viable in the 21st century than in the early 20th century. As medicine, nutrition, and general living conditions have improved, Americans are living longer and healthier lives. To illustrate that, here's the above chart, with male life expectancy at birth in each election year marked in grey, according to the Social Security Administration:

Much of the improvement in life expectancy at birth over the last century has come from greatly reduced infant and child mortality, and therefore may not be overly relevant to evaluating the prospects of politicians in the 60s and 70s.

In addition to life expectancy at birth, the Social Security Administration also provided life tables showing estimates for how many years the average male or female person of each year of age could expect to live for each decade going back to 1900. Using the closest year to each election, we found how many years each historical major party nominee, as well as the six Democrats vying for the 2020 nomination listed above, are statistically likely to live past Election Day, based on their age and sex:

Even though candidates have tended to get older, life expectancies have gotten longer, largely balancing each other out. That said, a 79-year-old man like Sanders in 2020 would have an average life expectancy of about 8.29 more years, according to the Social Security Administration. That would be the lowest of any major party candidate since 1900. Biden comes close behind, as a 77-year-old man would on average expect to live 8.29 more years. President Trump will be 74 on Election Day 2020, and the average 74-year-old man would expect to live 11.15 more years.

It's important to note that these are all actuarial average life expectancies. Every individual is different, and the particulars of one's life history and health situation are very large determinants in how long one will lead a healthy life.

That said, even though candidates have been getting older, and some of the top prospects in 2020s are pushing the historical boundaries on presidential age, rising life expectancies mean that old age isn't what it used to be.