Occasional reflections on Life, the World, and Mathematics

Posts tagged ‘generations’

The sins of the fathers

I was just reading Kevin Drum’s article on the fallout from the hapless US military raid in Yemen last week. He lists the costs:

Our adventure in Yemen last week failed to kill its target; caused the death of numerous Yemeni civilians; resulted in one dead American sailor; and ended with the loss of a $70 million helicopter.

This is not unusual of the commentary, and I find it weird that it fails to mention that a US civilian was among those killed: the eight-year-old daughter of American renegade Anwar Al-Awlaki, given that the sanctity of American life is the bedrock of American antiterror policies. I suspect this reflects the atavistic sense that the child of an evildoer is tainted, and somehow deserves to be punished for his crimes. Of course, the new president famously vowed to “take out their families”.

P.S.

My 8-year-old was telling me about a recent school lesson. The teacher was telling them (for some reason) about the use of the term P.S. Her explanation began “In the old times people didn’t have computers, so they had to write letters on paper…”

Of course, I know that my children have lived entirely in the age of personal computing, but it was still striking to hear it presented in such stark terms. I actually experienced the transformation exactly during my university studies. When I arrived at Yale in the fall of 1983 I had my Apple IIe, my roommate had a Compaq, and otherwise pretty much no one had a personal computer. Everyone else seemed to be writing their papers on a typewriter. (It was kind of unreasonable of me, actually, to expect the professors to read the low-resolution dot-matrix output that I turned in, but I wasn’t very considerate at the time.) The Macintosh appeared the next year, and by 1986-7 everyone was writing their senior essays on the Macintoshes in the college’s computer room.

Christmas Demography

Whereever I have lived in my adult life, the city has been extraordinarily quiet from Christmas to New Year’s — indeed, the quiet starts somewhat before Christmas. The natural explanation is that people go away for the holidays. (Students obviously do, but it’s far quieter than even at other times when students are on vacation.) The problem is, they must go somewhere, so it can’t be that every place empties out. (Obviously, some of the apparent quiet is simply the absence of traffic from people going to work, shopping, etc. When shops and restaurants close down in late December because of lack of customers it’s a bit self-fulfilling.) So why is it that I’m always in the places that people flee for the holidays?

A common pattern is that younger people with children travel to their parents, in their old home towns. In general, if there is a pattern of migration from some places X to other places Y, the sort of people who move around (like myself) will tend to be living at Y. At Christmas, then, the migration is temporarily reversed, and people travel from Y to X. For a brief time, Y empties out and X gets full.  (Even 2000 years ago Joseph and Mary had to go back to their home town for Christmas. And, as we know, the town was full up.) So, people like me notice that whereever they happen to be living is one of the places that empties out, because of the selection bias. People of my parents’ generation are generally living in places that take in visitors at Christmas, and so perhaps seem livelier than at other times of the year.

German politics in one sentence

In the context of the ongoing coalition negotiations in Germany, Spiegel quoted Mike Mohring, the leader of the CDU (center-right, the party of Angela Merkel, with a near-majority of the Bundestag seats) in the state of Thüringen speaking in favour of a coalition with the Greens, the environmental party, that started out as an insurgent far-left party in the 70s, but is now a disciplined party of the intellectual left. (Hence the need for the Pirate Party to fill the gap in the political spectrum by focusing on more up-to-date issues (not that the environment is ever not an important issue, but the well-heeled environmentalism of today’s Greens can shade into NIMBYism). Sadly, the Pirates didn’t clear the hurdle to make it into the Bundestag this time.)

Anyway, Mohring summarised the move of the Greens toward their “realistic” (Realos, contrasted to the Fundis, the leftist fundamentalists) wing by saying

Ein Großteil der Wähler der Grünen ist fest im Bürgertum verwurzelt.

A large portion of the Green voters is securely rooted in the middle class.

“Middle class” is only a weak translation for the German Bürgertum, with its undertones of right-thinking and class struggle. And the Greens (or rather, their voters) have not only made it, they are even “rooted”. There’s enough condescension to power a whole revolution right there (except that the Greens and their voters are too middle-class to revolt).

Stephen Wolfram’s longitudinal fables

There’s lots of interesting plots on Stephen Wolfram’s analysis of Facebook data, but what jumps out to me is the way he feels compelled to turn his cross-sectional data — information about people’s interests, structure of friendship networks, relationship status, etc. as a function of age — into a longitudinal story. For example, he describes this plotrelationship-status-vs-age2

by saying “The rate of getting married starts going up in the early 20s[…] and decreases again in the late 30s, with about 70% of people by then being married.” Now, this is more or less a true statement, but it’s not really what is being illustrated here. (And it’s not just the weird anomaly, which he comments on but doesn’t try to explain, of the 10% or so of Facebook 13 year olds who describe themselves as married.) What we see is a snapshot in time — a temporal cross section, in the jargon — rather than a description of how the same people (a cohort, as demographers would put it) moves through life. To see how misleading this cross-sectional picture can be if you try to see it as a longitudinal story of individuals moving through life, think first about the right-hand side of the graph. It is broadly true, according to census data, that about 80% of this age group are married or widowed. But it is also true that 95% were once married. In fact, if they had had Facebook when they were 25 years old, their Stephen Wolfram would have found that most of them (about 75%) were already married by that age. (In fact, about 5% of the women and 3% of the men were already in a second marriage by age 25.)

So, the expansion of the “married” segment of the population as we go from left to right reflects in part the typical development of a human life, but it reflects as well the fact that we are moving back in time, to when people were simply more likely to marry. And the absence of a “divorced” category masks the fact that while the ranks of the married expand with age, individuals move in and out of that category as they progress through their lives.

Of course, the same caveat applies to the stories that Wolfram tells about his (quite fascinating) analyses of structure of friend networks by age, and of the topics that people of different ages refer to in Facebook posts. While it is surely true that the surge in discussion of school and university centred at age 18 reflects life-phase-determined variation in interests, the extreme drop in interest in salience of social media as a topic is likely to reflect a generational difference, and the steep increase in prominence of politics with age may be generational as well. (I wonder, too, whether the remarkably unchanging salience of “books” might reflect a balance between a tendency to become less involved with books with age, cancelling out a generational shift away from interest in books.)

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