Twins

by Andrew Gelman on August 31, 2010 · 1 comment

in Baby

This story by Joshua Tucker on the popularity of the Polish twin politicians reminded me of these thoughts from a few years ago:

Curious about the latest statistics on twins (I had heard that they are more frequent in the context of modern fertility treatments), I did a quick google.

#1 was for the Minnesota Twins, but #2 was for Twins magazine. I clicked through to the magazine’s “Facts and Stats” section which indeed confirms that the birth rate for twins in the U.S. (as of 2002) was 1 in 32 babies, that is, 1 in 64 births, quite a big higher than the historical rate of 1 in 80 births.

But what really got me were its fun facts. They list 10 famous twins, which include Elvis Presley (of course), Ann Landers, John Elway, and 7 other people who really aren’t so famous. My guess of the least-famous of these is “Deirdre Hall, actress, Days of our Lives.” I mean, if twins really represent 1/40-th of the population (and they do), can’t they get 10 more famous people than this? Even Ann Landers really isn’t so famous as all that. And John Elway is a pretty impressive guy, but I certainly can’t believe he’s one of the 40 most famous athletes of all time. (He’s not in the Sports 100, for example.)

They also list some “Famous parents of twins,” a list which includes many truly famous people, including George W. Bush (of course), Bing Crosby, Pele, William Shakespeare, James Stewart, Robert De Niro, and Margaret Thatcher. A much more famous list throughout.

It’s interesting that their sample of famous twins (who represent roughly 1/40 of the population) is so much lamer than their sample of parents of twins (who presumably represent a very similar population fraction. Quick calculation: suppose that the average person has 2 kids, and each birth has a 1/80 chance of being twins. Then each person has roughly a 1/40 chance of being a parent of twins. Or another way of saying it: each pair of twins has 2 parents, so there will be roughly the same number of twins as parents of twins).

One might first attribute this to fertility treatments, causing a disproportionate number of modern celebrities to have babies, and twins, at advanced ages. But this wouldn’t explain George Bush, Bing Crosby, etc. My guess is that children of celebrities are more publicized than siblings of celebrities. Also, Twins magazine is clearly aimed at parents of twins, not twins themselves. But still I’d like to think that they could do better than mid-list actors…

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