Life Expectancy and Life Span: Definition & Factors

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  • 0:03 Late Adulthood
  • 1:00 Expectancy vs. Span
  • 2:26 Life Span Factors
  • 4:05 Lesson Summary
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Lesson Transcript
Instructor: Natalie Boyd

Natalie is a teacher and holds an MA in English Education and is in progress on her PhD in psychology.

Everyone wants to live forever, but the truth is that we all have only a limited time to be alive. In this lesson, we'll look at life expectancy and life span, as well as factors that can influence how long a person lives.

Late Adulthood

Susannah is 80 years old, much older than she ever thought she'd live! She's seen her kids have kids, and now even her grandkids have kids. Being able to meet her great-grandchildren is a special treat for Susannah, one that she is so happy that she was able to live long enough to see.

Susannah is in late adulthood, or the time of life after age 65. For those lucky enough to live into late adulthood, this can be an exciting time as they watch their family grow and find time after retirement for many of the passions they couldn't pursue during the busy earlier time in life.

But how likely is it that someone, like Susannah, can live into late adulthood? And is there anything she can do to increase that likelihood? Let's look at life expectancy and life span and factors that influence how long a person might live.

Expectancy vs. Span

When Susannah was born 80 years ago, no one ever thought that she'd live this long. Not because there was anything wrong with her, but because very few people at that time made it to age 80.

Life expectancy is the number of years the average person in a society lives. For example, the average life expectancy for babies born in the United States in 2014 is 79. The average length of time that a baby born in Sweden in 2014 can expect to live is 82.

In contrast, when Susannah was born in 1934, the average life expectancy was around 60 years old. That's a big difference! So, as you can see, both where and when you are born influence your life expectancy. But does that mean that all babies in America live two years shorter than all babies in Sweden?

Not at all! Life expectancy is just an estimate based on the statistics of that population. It is what the experts would expect to happen.

In contrast, life span is the length of time an individual person lives. It is the measure of the span of a person's life. So Susannah's expectancy might only be around 60, but we know that her life span is at least 80, and perhaps even longer!


Now that Susannah has great-grandchildren, she wants to stay alive even more than ever. Her goal is to live to see her great-grandchildren get married, which might be 20 or even 30 years from now!

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