You're older than you've ever been (and now you're even older)  

The New York Times has a piece on Social Security's predicitions for changes in life expectancy. A couple observations. The article doesn't go out on a limb to suggest what projected lifespans should actually look like, but the implication early in the piece seems to be that if lifespans rose by 30 years in the last century, they'll rise by a similar margin over the next hundred years. But it goes on to say that most of that change reflected decreasing infant mortality, which has basically no effect on Social Security (those who would have died get benefits if they live, but they also pay into the program for 40 years). The past 40 or 50 years are a much better benchmark for changes we'll see in the next century, but the article never indicates how much lifespans have changed over that period.

Also, we should probably keep in mind the fact that Social Security itself has had a huge impact on lifespans over the past century, and what we decide to do with it now will have an effect on lifespans in the next. Someone needs to run a regression to find out just how much of an effect Social Security has had, but my hunch is it's significant. Having a decent baseline income (and stress-free) changes your whole outlook, and at the beginning of the 20th century a huge proportion of American elderly were living in poverty.

No question though that we need to be considering lifespan estimates carefully, especially since major changes are in the works. And the predictions can be perilous: I'm reminded me of the article David Appell linked to here (apparently the link's lifespan is already passed) about Aubrey de Gray's prediction that a baby born in 2029 will have a lifespan of 5000 years. (You can see Aubrey de Gray's picture here.)

MORE: Something I've always wondered about life expectancy -- do the estimates for years past (ie the estimate for those born in 1976) change with time and technology? That is, does my expectancy get longer with each passing year not just because I've lived another year, but because of technological changes? Or is some projection of technological progress built into the life expectancy built into the estimate? (And if so, how well is that estimate tracking the actual march of technology?) The new year is almost here; I guess I've got mortality on my mind.