Not too long ago, I had a conversation with a journalist who was adamantly sticking up for her story in the face of criticism. The story included a statement of the form “X, says Y”, where Y was an anonymous source. Various other people were saying that X was not, in fact, true. But the journalist was standing firm. I then asked her whether she was standing firm on the statement “X, says Y”, which she reported — or whether she was standing firm on the statement that X. And here’s the thing that struck me: it took her a long time to even understand the distinction. A lot of American journalists stick the sourcing in there because they have to — but they very much consider themselves to be reporting news, and if X turned out not to be true, they would never consider their story to be correct, even if it were true that Y had indeed said that X.

Elsewhere, however, those conventions don’t hold. In a lot of political reporting, you have one person saying “X”, and another person saying “not-X”, and it’s left to the reader to decide whether one or the other or neither is telling the truth. And even facts can end up being attributed to people, which is even more confusing. Consider this, for instance, from a recent NYT article by Motoko Rich:

The home ownership rate has been falling from its peak of 69.4 percent in 2004, according to census data. By the fourth quarter of 2011, it was down to 66 percent. That means about two million more households are renting, said Kenneth Rosen, an economist and professor of real estate at the Haas School of Business at the University of California, Berkeley.

This is Rosen’s only appearance in the article, and he’s not being used to give an opinion, or an expert analysis: he’s being used to count rental households. And, at least on the face of things, he’s not particularly good at that. According to the 2010 census summary, there are 116,716,292 occupied housing units in America. So a basic back-of-the-envelope calculation would say that if the proportion of those units which went from owner-occupied to rented moved from 69.4% to 66%, then the increase in rental households would be 3.4% of 116,716,292, which comes to almost exactly 4 million. That’s double Rosen’s number.

Or, we can get more accurate, and go back to the 2005 American Community Survey, which showed 36,771,635 renter-occupied housing units in total. Contrast that with 2010, where there were 40,730,218 renter-occupied housing units. The difference, again, is almost exactly 4 million.

Most accurately of all, you can look directly at the Census Bureau’s quarterly estimates of the US housing inventory. According to that series, the number of renter-occupied houses in the US was 32,913,000 in the second quarter of 2004; it’s now 38,771,000. The difference there is not 2 million or 4 million but rather 5.9 million. (In the same time, the number of owner-occupied households has increased by 1.2 million.)

Now Rosen may or may not have good reason to believe that in fact the real increase in renting households is only 2 million rather than 4 million or 6 million. But if he does, that reason is not the drop in the homeownership rate from 69.4% to 66%. Not given the number of households in this country. (The homeownership data is here, by the way; it’s worth noting that Rich didn’t link to it.)

All of which housing wonkery is to say that even basic facts like the increase in US rental households can be non-trivial to pin down, and that both Rich and her readers would probably have been better off if she hadn’t bothered phoning Rosen at all, and had just got her numbers for the increase in rental households directly from the people measuring such things. Citing sources doesn’t help the reader at all, here: if Rich had been forced to assert the increase in rental households, rather than simply attributing the number to Rosen, then she would probably have got something closer to the truth.

The difference between linking and citing is the difference between showing and telling. I’m not a big fan of citing, mainly because it gets in the way: we might learn a lot about where the Haas School of Business might be, but at the same time we’ll learn nothing useful about the increase in the number of rental households. On the other hand, if Rich had simply said that “about six million more households are renting”, complete with hyperlink, that would have been shorter, more useful, and more accurate, even if there were no explicit citation.

Felix Salmon is an Audit contributor. He's also the finance blogger for Reuters; this post can also be found at Reuters.com.