Life Expectancy

     It's nice to know that I'm not the only person out there who cares about misrepresented statistics:

(Matthew Zeitlin guest posting on Jonathan Chait's blog in response to a huge mistake made by the New York Times columnist Charles Blow).


   I recommend reading the whole post, since Zeitlin does a great job with it.


   I also want to say a word about life expectancy as a statistical concept when applied to public policy, since I feel Zeitlin doesn't quite go far enough, and survival analysis is subject to a lot of media abuse (abuse that I expect will continue during the 2012 elections, alas).  One line that I keep hearing again and again in the media from people who style themselves as "Serious Thinkers on Fiscal Matters" (people who praised Paul Ryan's "Roadmap" I'm looking at you), is something like this: "Social Security is a ticking time bomb.  Nobody ever anticipated in the 1930's that old people would live well into their 70's and 80's.  You retired at 55 and croaked by 60.  So we must impose drastic benefit cuts now in order to keep the system solvent."  It's definitely true that infant life expectancies in developed nations have improved markedly since the 1930's.  A boy born in 1940 had a life expectancy of 60.8 and a woman born in the same year could expect to live to the age of 65.2.  Had those two babies been born as I write this post (using the SSA's mortality calculator), they could expect to live to 82.2 and 86.1 respectively.  These gains are enormous, and represent a great societal achievement.  However, this increase is mostly not because the elderly are living longer; it's mainly because of the incredible reductions in child mortality that occurred during the 20th century.

    For a detailed story of how public health officials in the US defeated the scourge of infant mortality, c.f. this link.  Suffice it to say that while in 1940, the US infant mortality rate was 50 per 1000 live births (already down from 100 per 1000 live births in 1900!), that same figure had plummeted to about 7 deaths per 1,000 live births by 1990, where it more or less remains to this day.  The CDC link that I provided above has more details than I do as to why this occurred, but it is mainly due to advances in sanitation, urban planning, nutrition, family planning, vaccines, and antibiotics.
    The more relevant question when talking about life expectancy in this context is what the life expectancy of an adult is, and here's where the arguments made by the talking heads start to look a little fishy.  In 1940, a man who had survived to the age of 65 could expect to live an additional 12.7 years, while a woman who had reached 65 could expect to outlive her male counterpart by about 2 years.  Fast forward to 2011, and our hypothetical male/female pair could expect to live another 18.7 and 20.8 years respectively.  Definitely a respectable gain, but not earth shattering in the same way that we're often led to believe by pundits discussing the fiscal challenges of Social Security; each gender has gained about 6 years of life expectancy if they reach the age of 65.  The real fiscal challenge facing Social Security (and European pension systems for that matter) is mostly due to the fact that as the baby boomers retire, the ratio of workers to retirees will move in an unfavorable direction, not due to misleading mortality statistics.