Evidence at the Upshot

March 31, 2018
Posted by Jay Livingston

“Common sense” is not evidence. Neither is “what everyone knows” or, to use a source of data favored by our president, what “people say.”  That’s one of the first things students hear in the intro sociology course. Our discipline is empirical, we insist. It is evidence-based, and evidence is something that really happened. Often you have to actually count those things.

The Upshot is the “data-driven” site that the New York Times created to compete with FiveThirtyEight. Friday, an Upshot article about marriage, social class, and college had this lede,* a six-word graf.*

Princetonians like to marry one another.

The article, by Kevin Carey, showed that students from wealthier families are more likely to be married by their early thirties than are students from the bottom fifth of the income ladder. Carey argued that the cause was “assortative mating” – like marries like – and that the pattern holds even for graduates of the same elite school – Princeton, for example. Rich Princetonians marry other rich Princetonians, says Carey. Poor Princetonians remain unmarried. In their early thirties, only a third of them were married.

(Click on the image for a larger view.)

According to Carey, the sorting that leads to mating takes place in the “eating clubs” – Princeton’s version of fraternities and sororities. Acceptance into this or that club depends in part on social class, so as Carey sees it, “Eating clubs are where many upper-income marriages begin.”

It’s logical and it makes sense. The only trouble is that Carey provides no evidence for Tiger intermarriage. That 56% of rich Princeton alums who were married by age 32-34 – we don’t know who they married. Another rich Princetonian? Maybe, maybe not. We know only that they were married, not to whom.

Oh, wait. I said Carey provided no evidence. I take that back. Here’s the second graf.

Although the university is coy about the exact number of Tiger-Tiger marriages, Princeton tour guides are often asked about matrimonial prospects, and sometimes include apocryphal statistics — 50 percent! Maybe 75! — in their patter. With an insular campus social scene, annual reunions and a network of alumni organizations in most major cities, opportunities to find a special someone wearing orange and black are many.

You don’t have to have taken a methods course to know that this is not good evidence, or even evidence at all. What people say, and even logical reasons that something should happen, are not evidence that it does happen. Carey all but admits that he has no real data on Princeton intermarriage, but that doesn’t stop him from writing about it as though it’s a solid fact.

Is it? Five years ago, a Princeton alumna, president of the class of ’77, published a letter in The Daily Princetonian giving her 21st-century counterparts this bit of advice: “Find a husband on campus before you graduate.”

The reaction was swift and predictable. Some even thought that the Princetonian had run the piece as an April Fool’s joke. Besides, people these days typically do not get married till their late twenties – at least five years after they graduate. A lot can happen to that eating-club romance in those five years.

Let me clear: the negative reaction to the letter and the median marriage age of the US population are not evidence that Princetonians are not marrying one another. But it’s just as good (or bad) as Carey’s evidence that they are.

---------------
*Using journalism jargon when I’m writing about journalism is one of my favorite affectations.