Thursday, August 19, 2010

Ray Fisman and the Tierney Ratio

The Tierney Ratio (sometimes called the Tierney Test because people love alliteration) is a measure of journalistic mediocrity named for its frequent subject, John Tierney. You find the Tierney Ratio of an article by counting the number of words it takes to address all of the significant problems in the article, then dividing that by the article's word count.

As you might expect, Tierney Ratios vary greatly from author to author. The sorely-missed Olivia Judson maintained a TR of virtually zero while writing for the New York Times while John Tierney, a science writer with no appreciable background in or aptitude for science, routinely had observed TRs in excess of one or two. (it is possible that Judson was kept in the Op-Ed rather than Science section out of concern that she would unfairly lower the latter's average.)

The value of the Tierney Ratio is somewhat limited by its serious data censoring problem (analogous to this well-known example). Faced with articles and essays of sufficiently low quality, researchers are almost always forced to leave significant mistakes, distortions and fallacies unaddressed.

Which brings us back to Ray Fisman's recent column in Slate, which reaches an almost Hellmanesque level of inaccuracy. Getting a true TR on something like this is an extraordinarily tedious job so the readers who aren't into hardcore education wonkery might want to skip the next few posts. You'll know it's safe to come back when we start posting Daily Show clips again.


  1. Er, did you forget a "minus one" at the end of your definition of the ratio? Or should Judson's ratio be 1 and Tierney's be "in excess of [two or three]" instead?
    As it is, if Judson's ratio was 0, either she wrote articles that required no words at all, or she wrote infinitely-long articles... whereas Tierney's ratio of just a bit more than 1 sounds very reasonable.

    Anyhow, I haven't read enough Tierney to have an opinion, but yes, Judson's articles are (were?) great!

  2. Probably should have been clearer (unless I've gotten myself completely turned around). The numerator is the number of words you (or some third party) would have to write to correct the flaws in one of Judson's articles. It is possible that you won't be able to find any significant flaws (I generally couldn't). If so the TR of her article would be zero.

    By comparison, here's a passage by John Tierney in an editorial on how we can have cheap manned exploration of space:

    "For decades NASA's doctors have been trying to find some physical therapy to mitigate the effects of weightlessness, but astronauts can still barely walk after six months of it. Meanwhile, NASA has largely ignored an obvious alternative: redesign the spaceship instead of the human body. Artificial gravity could be created during the flight to Mars by twirling the ship."

    This entire article clocks in at under 800 words but it would take at least that many just to explain to a lay audience why this "twirling" solution would require a ship with a huge radius (if you want to work it out yourself, the key that there can't be a perceptible difference in an object when raised over your head and that objects dropped near each other should appear to fall along parallel paths.)

    That paragraph alone pushes the TR over one.


    p.s. Judson says this is just a sabbatical so there's still hope. In the meantime, I wonder if they could get Ian Stewart.

  3. Ah, I see. I had thought your numerator's "significant problems" meant "the important topics the original author chose to write about".
    But you meant "the mistakes in the original article". My bad!

    I definitely agree that science writers ought to demonstrate an understanding of the science they're trying to describe...