Hi

A fantastic site for looking at this kind of data over time and for many 
countries is www.gapminder.org.

One way that you can get some idea about the issues raised by Mike is to look 
not only at statistics like life expectancy at birth, but also at child 
mortality rates, which is a major factor in longevity (thank heavens for Joseph 
Lister, vaccines, ...!).

As to the increased longevity of higher SES women and not lower, the decrease 
in smoking rates has been much greater for higher SES than lower SES, thus 
producing an even more marked relationship between SES and mortality than 
existed earlier.  The NY Times had a piece on that a few years ago.

Take care
Jim



James M. Clark
Professor & Chair of Psychology
[email protected]
Room 4L41A
204-786-9757
204-774-4134 Fax
Dept of Psychology, U of Winnipeg
515 Portage Ave, Winnipeg, MB
R3B 0R4  CANADA


>>> "Mike Palij" <[email protected]> 24-Mar-13 6:59 PM >>>
The NY Times Sunday magazine has an interesting article on
life expectancy and the factors that affect it. See:
http://www.nytimes.com/2013/03/24/magazine/who-lives-longest.html?hpw&_r=0 

It starts off with saying that a Swedish baby born in 1800 had
a life expectancy of 32 years -- Sweden was the first country
to keep extensive records of births and deaths and allowed one
to calculate such a value.  Now, to tell the truth, I don't know
if "life expectancy" as reported here is a simple descriptive
statistic (i.e., mean or median time to death) or is calculated in
some other way but the article goes on to point out how misleading
this value is *if one considers it as a point estimate*.  Because
so many infants and children died early in life, the implication
is that the distribution of the variable "age at time of death" is
a seriously positively skewed distribution (whether it a skewed
normal or some other distribution is an empirical question that
is not addressed).  What is missing is a measure of variability
for "age at time of death", something like the simple range but
that is likely to be uninformative (e.g., what is one to make of
the range 0-70?).  The interquartile range might be more informative
because it would represent that age range for the middle 50%
which would be more informative (one could also argue that
if the above life expectancy of 32 years is the arithmetic mean,
then perhaps some robust measure of central tendency should
be used).

So, for pedagogical purposes, the article provide a basis for
comparing an argument based on a point estimate (like the
life expectancy of 32 years) versus an interval estimate like
the interquartile range or some other measure of variability.
The rest of the article is also of interest because it goes into
why a measure like life expectancy, beyond the point vs.
interval distinction, is problematic because it might cause one
to focus to much on longevity and how to increase instead of
focusing on other factors that influence it, for example, the
article's example of white women with college degrees having their
life expectancy increase by 3.5 years during the period of 1990-2008
while women without a high school diploma lost 5 years.
How does one fix that?

-Mike Palij
New York University
[email protected] 




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