
"Life Expectancy" Doesn't Measure How Long You're Expected To Live - elmarks
http://blog.edwardmarks.com/post/31337304505/life-expectancy-doesnt-measure-how-long-youre
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tptacek
This is a great post. Because I'm a nerd, I'm compelled to make an orthogonal
point:

Life expectancy is not entirely medical and is not a particularly good way to
compare countries. Consider that among the top causes of death in the US are
"accidents" (predominantly motor vehicles) and suicide, both of which are
anomalously high in the US.

Consider also that if you go to the top US cause of death (heart disease,
clearly medical) and then compare the world rankings for heart disease deaths,
you'll find many of the countries that beat the US in the life expectancy
rankings do worse than the US in the heart disease mortality rankings.

You'll tend to see similar effects for other medical issues, particularly
cancer, in which the US notoriously outperforms many of the European countries
that outrank it on life expectancy.

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tesseractive
I haven't studied the data, but I would be surprised if motor vehicle deaths
were "anomalously" high. My hypothesis would be that it is an entirely
expected outcome given the comparative lack of public transportation in this
country relative to other industrialized nations such as Japan and those in
Europe. More driving miles (or, perhaps, more hours spent driving) per capita
should lead to more motor vehicle accidents. And if the streets and highways
are more crowded than in other countries, it might scale faster than linearly.

Though if what you meant was that motor vehicle accidents were not a good
reflection of the quality of our medical care, I expect that would be a fair
assessment.

~~~
tptacek
It's easier to maintain a dense public transportation system when the system's
goals are (for instance) to move 80MM people around in an area the size of
Colorado. Colorado, by comparison, has a population of 5MM.

But yes, I was making the latter point.

Does life expectancy tell us _something_ about the differences between life in
the United States and Finland? Yes... but what if all it's telling us is "the
United States is simultaneously less dense and comparably urban to Europe"?

~~~
tesseractive
I wouldn't expect, say, Wyoming to have a well developed public transportation
system, or even Colorado as a whole. But once you get past a fairly small
number of major cities, our public transportation systems for metropolitan
areas are still underdeveloped.

Colorado's front range, for example, would almost certainly benefit from
having a well-developed commuter rail system, with heavy passenger rail
connecting the corridor from Colorado Springs to Fort Collins (with a spur to
Boulder) and light rail taking people from the terminals to points spread
further out.

Doing something like this would take a long time and cost a lot of money, but
our choice (so far) not to spend that money in most metro areas has a direct
effect on the quality of life in this country.

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akgerber
Fortunately, it isn't wholly hopeless in this country.

The Front Range is indeed making a large investment in commuter rail, though
not yet all the way to Colorado Springs & Fort Collins: <http://www.rtd-
fastracks.com/systemmap.php>

The Los Angeles area is likewise making significant investments in its rail
system.

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baltcode
Other than the cohort and period life expectancy, what is imp. to most people
should be something else:

* How many more years do you expect to live if you are already X years old in 2012?

This is obviously different than just calculating from the cohort life
expectancy of 2012-X since you you've already passed the vulnerable infancy
stage. Also, say you are 90 today, so your cohort exp, for 1922 births must be
something like, say 80. Your expectation of living more is certainly not -10
years!

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yesbabyyes
A very interesting post indeed. Another common mistake many people seem to
make is when comparing historical life expectancies. Most of our progress in
prolonging human life is due to minimizing the infant mortality rate. This
means that people who survived infancy and childhood could make it to an old
age even in historical times.

~~~
refurb
This is true and a huge annoyance to me when people say "When social security
was first put in place, most people didn't live to collect it!"

This is of course false. Back in the early 1900's when life expectancy was
only around 60, if you survived your childhood, you'd likely live to 70 or 80.

~~~
danielweber
_Back in the early 1900's when life expectancy was only around 60, if you
survived your childhood, you'd likely live to 70 or 80._

This didn't seem right so I checked. A 20 year old in 1900 could expect to
live to 62. In 1939 (4 years after SS was first put in place) a 20 year old
would live to 67.

Interpretted as a median age of death, you are right that more than 50% of 20
year-olds collected at least 1 check, but a significant fraction died before
retirement age, and they generally didn't say in retirement for decades.

<http://www.infoplease.com/ipa/A0005140.html> I used white males, and women
lived longer but non-whites lived shorter.

~~~
refurb
Thanks for looking up actual numbers!

I guess my point also has to do with what "averages" mean. In 1939, a 20 year
old might _on average_ live to 67, but that means a number would die at 47,
but a similar amount would live to 87.

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eranki
Also life expectancy changes as you age:
<http://www.ssa.gov/oact/STATS/table4c6.html>

By the time you hit 60, you've gone from ~75 to ~80.

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csense
I don't like using averages because they can be misleading. A triplet of the
25th, 50th and 75th percentiles is more descriptive. Of course, the most
complete picture is looking at the whole distribution.

I'd like to see a plot of the distribution of lifetime as a function of birth
year. I.e. a 3D plot with current age on the X axis, age of death on the Z
axis, and probability on the Y axis. (Where, as in Minecraft, X is east/west,
Z is south/north.)

Cut off the portion representing people who have died already (Z < now-X),
renormalize each cohort so its Y values add up to 1, and you'll get the
distribution of lifetimes for people who are alive today. (I.e. a conditional
distribution, conditioned on being alive today.) Which at least one other
poster was asking about.

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tokenadult
Just last week there was another Hacker News post that prompted me to look up
some of the articles by demographer James W. Vaupel, one of the leading
scholars on the demography of aging and how to adjust for time trends in life
expectancy. His article

"Biodemography of human ageing" Nature. 2010 Mar 25;464(7288):536-42.
doi:10.1038/nature08984

[http://www.demographic-
challenge.com/files/downloads/2eb51e2...](http://www.demographic-
challenge.com/files/downloads/2eb51e2860ef54d218ce5ce19abe6a59/dc_biodemography_of_human_ageing_nature_2010_vaupel.pdf)

covers most of the essential issues. His striking finding is "Humans are
living longer than ever before. In fact, newborn children in high-income
countries can expect to live to more than 100 years. Starting in the
mid-1800s, human longevity has increased dramatically and life expectancy is
increasing by an average of six hours a day."

[http://www.prb.org/Journalists/Webcasts/2010/humanlongevity....](http://www.prb.org/Journalists/Webcasts/2010/humanlongevity.aspx)

Meanwhile, a person at any given age can look up period life tables for what
the blog post author of the post submitted here correctly describes as a
MINIMUM life expectancy at that person's current age.

<http://www.ssa.gov/oact/STATS/table4c6.html>

<http://www.infoplease.com/ipa/A0005140.html>

(The links shown are for United States data, but data like these are available
for most developed countries.)

It is also possible to find life expectancy formulas adjusted for personal
health status and lifestyle.

<http://www.msrs.state.mn.us/info/Age_Cal.htmls>

(Minnesota data)

[http://www.bupa.com.au/health-and-wellness/tools-and-
apps/to...](http://www.bupa.com.au/health-and-wellness/tools-and-apps/tools-
and-calculators/quick-health-age-check)

(Australia data)

The link posted last week

[http://www.scientificamerican.com/article.cfm?id=longevity-w...](http://www.scientificamerican.com/article.cfm?id=longevity-
why-we-die-global-life-expectancy)

gives good data on trends in causes of death from 1960 to the present in the
United States and in OECD countries as a whole. It showed that life expectancy
at birth, at age 40, at age 60, at age 65, and at age 80 have all increased
during the years shown on the chart.

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JumpCrisscross
The "rectangularisation of the life curve", i.e. a cohort facing low mortality
(thanks to better social practices and healthcare) until a ripe old age when
it starts dramatically dying off, implies a maximum human lifespan that we
have not significantly manipulated in the history of human biology.

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xm1994
Thanks for making me realize I've been using life expectancy tables
incorrectly for most of my life.

One comment regarding the yearly progress of the cohort rate. I would think
this would fluctuate with significant medical advances (e.g. the first few
years that bypass surgery/artificial hearts started to be used). I can't see
how medical progression is perfectly linear at 1.0%/year.

~~~
Tyrannosaurs
I think you're overestimating the number of people who benefit from even a
major advance.

In the UK (population 70 million), 28,000 heart bypass operations happen per
year. The number of people who will have one is in the low single digits as a
percentage of the population.

Even for those people who do have one there is no guarantee that it will have
a significant impact on their lives. Yes for some it will but for others it's
only reduced one possible cause of death and a lot of the behaviours that lead
to heart problems also lead to, say cancer, or diabetes, or liver failure, or
something else that will cut your life short.

Then compare that to the thousands of small improvements.

I can see it might not be constant over an extended period, but I don't think
there are many, if any, things that would cause a significant spike.

~~~
ef4
> I can see it might not be constant over an extended period, but I don't
> think there are many, if any, things that would cause a significant spike.

While it's hard to predict, I personally wouldn't bet against a game changing
spike in the coming decades. It's only very recently that medicine has started
riding Moore's law. Robotics and miniaturization are speeding up basic
research by orders of magnitude.

I don't think it's unreasonable to say that biology has achieved more in the
past two decades than in all preceding history. And there's no sign that the
exponential is running out.

Granted, there may be fundamental limits that we don't appreciate yet. That's
the whole draw of science, we simply don't know.

~~~
Tyrannosaurs
Interestingly I think the one thing that would cause a spike happened outside
the last two decades - the discovery / development of antibiotics.

You may be right but there will still be bottlenecks in the process around
patient trials and the more "manual" stages of any treatment.

I think the next big improvement will likely not register on life expectancy
because it will be in response to a specific problem. The next generation of
anti-biotics for instance will have a massive impact but will likely only
cancel out the negative impact of drug-resistant strains of bacteria.

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Groxx
Site seems to be down, Google cache:
[http://webcache.googleusercontent.com/search?q=cache%3Ablog....](http://webcache.googleusercontent.com/search?q=cache%3Ablog.edwardmarks.com%2Fpost%2F31337304505%2Flife-
expectancy-doesnt-measure-how-long-youre)

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grecy
When looking at these numbers, and thinking how the official retirement age in
most countries has been raised to 67 or 69, does anyone else feel like old
Boxer from Animal Farm [1] ?

They keep dangling that retirement carrot in front of us, but by the time we
get to enjoy it, we're dead.

[1]en.wikipedia.org/wiki/Boxer_(Animal_Farm)

