WSI: Life Expectancy

Demographers commonly use life expectancy rates as a measure of societal well-being. The life expectancy rate is the years someone is expected to live when born based on actuarial science. Long life is a universal indicator of prosperity across cultures and time. It is an important measure to demographers because achieving it requires a complex mix of variables, like a sustained nutritious food supply, a sanitary and safe environment, relatively little disease, the absence of war, and a stable society.

So what can we say about this measure of prosperity throughout human history? Here are estimates of two social scientists and economists typical of those who study these issues:

For most of its existence, Homo sapiens lived in far-flung hunter-and-gathering communities, each of which was quite small and barely able to reproduce itself. Life expectancy at birth was hardly twenty-five years on average, and those persons who survived childhood often died violently, in combat with other hunters, at relatively young ages. (Robert William Fogel, The Fourth Great Awakening and the Future of Egalitarianism, 48)

For much of human history, average life expectancy used to be 20-30 years. By 1900, it had climbed to about 31 years … By 2003 it was 66.8 years. (Indur Goklany, The Improving State of the World, 31)

To put the last statement by Goklany in perspective, let's graph the estimated life expectancy on a chart:

If we show only the last two centuries, we get a clearer picture of what has happened:

Using life expectancy as a measure of prosperity, the world is far more prosperous than ever, and the gap is narrowing between the top and bottom rungs of the global community. More amazing, most of this change occurred over a time when the total world population grew sixfold, from less than 1 billion in 1800 to about 6.6 billion today!

This is not to say that every nation, or every region within a nation, or every subgroup within a nation, has prospered equally well. Note the tragic impact of the AIDS epidemic and social chaos has had on sub-Saharan Africa by looking at this map of life expectancy from Wikipedia:

The trajectory of change is an unprecedented rise in prosperity. It is uneven growth, but every corner of the planet has improved, and the gap between top and bottom nations is closing.

Next, we look at infant mortality rates.

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Comments

[Danny Gamache]

One way I teach students the historical context is to use the videos by Hans Rosling from TED. Here is one:

http://www.ted.com/index.php/talks/hans_rosling_shows_the_best_stats_you_ve_ever_seen.html

[Michael W. Kruse]

Danny, I've linked this vid twice in the past and will again in couple more posts. :) Great stuff.

[Seth]

Mike,
I'm not sure I can agree with that version of the history of life expectancy in the world. I think its in Psalms that David says that a man generally lives 70 years, or "if by reason of strength, 80 years. And we know from many old testament books how long people lived then. It seems to me that a U shaped chart would be more appropriate... what do you think?

[J]

Those advances always startle me when I see them on paper. This is another good one from Greg Clark's A Farewell to Alms.

Any thoughts on the view of Collier and others that the current global economic scene is increasingly characterized by a large group of 5 billion prosperous and prospering peoples starkly contrasted with another group of one billion, the poorest of the poor, whose prosperity and life expectancy are stagnant if not declining?

[Michael W. Kruse]

Seth, the stat here is life expectancy at birth. So if I say life expectancy is thirty, then what I'm saying is that half the people born will only live to be thirty or less. Half will longer, tappering off toward some upper limit.

As will be seen in the next post, infant mortality (children born that die before age one) has a significant impact on life expectancy. Historically, between 1/4 and 1/3 of children died before age one. Therefore, life expectancy at age one was longer than for at age 1 and possibly longer than at age 5.

I understand the Psalms reference to be about the upper limits of how long an "old person" might live.

As the characters in in Genesis 1-11, assuming this was intended as a precise accounting of historical events, I presume they existed well before 10,000 BCE. We have sufficient historical data to make estimates going back 4,000 to 5,000 years and good reason to make assumptions about the few thousand years preceding. So if it is a U, it has are really wide bottom. :)

[Michael W. Kruse]

J, I noted Collier's book in my introduction (see index link, top right column) to the series. I'm going to turn to it once I finish presenting these various trends.

[Simon Fowler]

Thanks for doing this series, and all your incredibly insightful thoughts and analyses. I really appreciate your approach and the grace of your interactions.

Your perspective and questioning has been extremely helpful to me as I've thought through and discussed matters of poverty and economics with others.

First time posting a comment here but I've been reading you for some time here and in the many conversations over at Jesus Creed.

Grace to you.

[Michael W. Kruse]

You're welcome Simon and thank you for your kind affirmation. Writing about this stuff helps clarify these things in my mind. I'm glad you find this helpful too.

Peace to you.

[J]

Michael - Thanks. Some how I missed your intro post, I'm looking forward to your thoughts.

[ZZMike]

"The Global Life Expectancy" graph: aha!! the Hockey Stick Model confirmed!!

PS: the end of the Hans Rosling URL is missing - I found it:

Best Stats

... but I couldn't get it to play all the way through from here. It stopped dead about 1 minute in.)

There are some amazingly good pieces in there - Muray Gell-Mann, for one, Ray Kurzweil, and even that rotund gentleman who wants us to believe that the Sky is Falling (in the guise of Global Warming).