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In this article, About.com article on Life Expectancy they claim:

In 1900, the world life expectancy was approximately 30 years

I've also the same claim elsewhere.

However, this doesn't jibe with informal data-gathering I have done:

  • An arbitary search of Wikipedia of random people that I know lived and died (of natural causes) before the 20th century shows that almost all of them died over 30.

  • I was in an old cemetery the other day, and saw that very few of the people buried there pre-1900 was under 30 years.

So I understand my "research" is purely unscientific - e.g. to be on Wikipedia you have to be famous, which means you probably were wealthy, which means you probably increased your chances of living longer.

Still, I find it hard to imagine a world where 30 is the life expectancy - i.e. that roughly around half the people would die younger than 30.

I would like to hear further evidence supporting this fact or explanation for the fact.

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    Maybe infant mortality rate was averaged in with the number. I never felt that number sounded right either. – David Mar 27 '11 at 0:44
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    @Sklivvz - i would disagree with "the single most significant", but it's certainy impactful. The actual analysis of mortality decrease due to different medical advances (Antiseptics, vaccines, antibiotics, transplants, etc...) would make for an interesting question, though possibly off-topic for Skeptics. – user5341 Mar 27 '11 at 14:40
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    Biographies of random people would have a serious selection bias, in that they'd be written about people who lived long enough to accomplish something significant. Now, some significant people died before 30 (Keats comes to mind), but it completely eliminates infant mortality and childhood disease from the figures. – David Thornley Apr 7 '11 at 2:10
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    @DVK: I'd suggest that basic hygiene was likely a major breakthrough, changing cities from population sinks to population sources. The Panama Canal Zone was one of the world's worst fever coasts before the preparation for building the canal, and that predates most useful drugs. – David Thornley Apr 7 '11 at 2:12
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    The fact that you're talking about world life expectancy is not helpful either. Even now, I wouldn't expect it to be the 80+ years that the industrialized west can typically expect, because there are still large parts of the world where it doesn't rise above 35. In 1900, Japan and Korea were only just industrialized for example, and Africa... well, was simply a place from which Europe extracted natural resources. That doesn't even touch the other wild parts of the world, many of which Westerners avoided entirely for being too dangerous. – Ernie Jun 14 '11 at 20:51
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If you want to look on Wikipedia, here's a good place to start:

Table of Life Expectancy Variation Over Time

The table clearly shows that pretty much till mid-20th century, life expectancy was <30 years (aside from aristocracy).

As to why such a change in the last 100+ years, there are 3 main factors:

  • Child/infant mortality. From the same Wikipedia article:

    The percentage of children born in London who died before the age of five decreased from 74.5% in 1730-1749 to 31.8% in 1810-1829. Ref 1;Ref 2

    Even 30% infant mortality means that the "actual" life expectancy of, say, 50 years would turn into average TOTAL life expectancy of 30+ years. (Basic math - for population of 10 people, average life expectancy would be roughly (3*0.5+7*50)/100=351.5/10=35.15. This is VERY rough and not an actual statistical calculation accounting for distributions, but enough of an approximation to show the great effect on the #s)

  • Medicine. Most life-extending medical advances we take for granted are, at most, 120-150 years old (including antibiotics or, heck, sterilization). See this Timeline of Medicine and Medical Technology. A few among the late-19th/early 20th century are 1870-80s (Antiseptic practices, germ theory of disease, first vaccines by Pasteur); 1906 (Vitamins), 1928 (Penicillin).

  • Widespread growth of the average wealth of society (e.g. economic surplus) allowed people who wouldn't have survived before 20th century (e.g. die of hunger/malnutrition/lack of vitamins/etc...) to survive. Before 19th century, a VERY large proportion of population live basically on the edge of subsistence.

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    also see Life_expectancy_vs._life_span on the same page: "Life expectancy is often confused with life span to the point that they are nearly synonyms; when people hear 'life expectancy was 35 years' they often interpret this as meaning that people of that time or place had short life spans." and "in the Roman Life Expectancy table at the University of Texas where at birth the life expectancy was 25 but at the age of 5 it jumped to 48." – matt wilkie Mar 27 '11 at 7:55
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    @DVK - What I meant is that Wikipedia is generally not authoritative enough. – Sklivvz Mar 27 '11 at 15:33
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    @Sklivvz - agree. Only the pieces that cite other research are. – user5341 Mar 27 '11 at 16:50
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    @Sjoerd: No, life expectancy at birth has nothing to do with lifespan. While it may be common for people to live well into their 50s and 60s, if 75% of your children die before the age of 5 (which was common even in wealthy, industrial countries before 1700), that's going to drag the average life expectancy down quite a lot. – Ernie Jun 14 '11 at 20:40
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    Yes, but that's exactly what they mean when they say "average life expectancy". If it's really low, like around 30, then they're clearly counting infant mortality rates, which was the largest factor in people dying throughout most of history. The ancient Greeks had plenty of citizens who lived to be a ripe old age, but their average life expectancy was very low due to high infant mortality rates. You could likewise say that most people died before the age of 30 (thus the average). And that was largely because of high infant mortality rates. – Ernie Jun 15 '11 at 16:22
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I don't think this data is available on a world scale. Remember, many countries didn't do any census stuff before the start of the previous century, and many still don't. Wolfram Alpha has some data available. This one, for instance, is the life expectancy at birth for The Netherlands:

enter image description here

See the impact of the two world wars? Interestingly, the Netherlands didn't even participate in WWI...

The US data Wolfram has, starts in the 1930s:

enter image description here

UK:

enter image description here

Iceland:

enter image description here

You can try some more countries for yourself, but most countries don't have data before the '40s (at least not in Wolfram Alpha's database)

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I'm willing to bet infant mortality had something to do with it. If you have a person who died at 70, and a person who died shortly after childbirth, and those 2 are your sample basis, the average life expectancy is 35.

I know this source is dubious, but http://www.cdc.gov/mmwr/preview/mmwrhtml/mm4838a2.htm . This is a CDC document that covers the infant mortality rate in the US since 1900. It states that the infant mortality rate was over 10% in the US as of 1900. That's going to be a major drain on life expectancy. "And women dying in childbirth is going to lower numbers too".

  • I think this is already covered in the accepted answer. – Suma Jun 29 '15 at 9:20
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I found quite interesting paper from 1994 by Michael R. Haines Estimated Life Tables for the United States, 1850-1900.

According to that paper, life expectancy in US 1850 was 38 years. I would say that 30 years for all world at 1900 is maybe bit low, but plausible.

What else could we see from life table of US 1850?

  1. Child mortality has high impact. 23% of newborns were dying during 1 year.
  2. Median life expectancy was higher than average life expectancy.
  3. Mode of age of death (excluding children) was much higher, than average or median.
  4. If someone reached age 20, he had 90% probability to reach age 30.
  • There may also have been some advancements in medicine between 1850 and 1900. This does not really address the question sorry. – Chad Jun 29 '15 at 20:32

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