We know that the much-discussed increase in mortality among middle-aged U.S. whites is mostly happening among women in the south.
In response to some of that discussion, Tim Worstall wrote:
I [Worstall] have a speculative answer. It is absolutely speculative: but it is also checkable to some extent.
Really, I’m channelling my usual critique of Michael Marmot’s work on health inequality in the UK. Death stats don’t measure lifespans of people from places, they measure life spans of people who die in places. So, if there’s migration, and selectivity in who migrates where, then it’s not the inequality between places that might explain differential lifespans but that selection in migration.
Similarly, here in the American case. We know that Appalachia, the Ozarks and the smaller towns of the mid west are emptying out. But it’s those who graduate high school, or who go off to college, who are leaving.
It’s possible, but obviously not certain, that the rising death *rates* are simply a reflection of this selectivity in migration.
I replied: This could be true, I’m not sure. I haven’t tried to crunch the numbers to see if mobility is enough to cause these changes, but on first glance it seems possible. One thing also to remember is that when comparing a particular age category over several years, we’re not comparing the same people. Today’s 50-yr-olds are not the same as next year’s 50-yr-olds. So the usual challenge is separating age, period, and cohort effects. But I agree with you that mobility is an issue too. On a related point, I questioned Case and Deaton’s comparisons by education category, because the proportion of people with college degrees etc. in different age groups has been changing over time too.
Worstall replied, “Not sure when the switch took place in the US but in my age cohort in the UK some 12% or so went to university, now it’s near 50%.” And then he followed up:
Further to the point that migration might be explaining something about these changes in average lifespans. Interesting new research from Glasgow. Seems that it at least part of the story there.
I guess the point is that death rates below age 65 are low enough that it doesn’t take much migration of at-risk people to move the numbers around.
P.S. As an aside, it’s kind of amazing that the big discussion of mortality trends was over a year ago. It seems so recent! There’s so much going on in statistics and social science, room for 400 or so posts a year, sometimes it’s hard to see how we can possibly keep it all in our heads at once.