Screamers Gone Awry: The Availability Heuristic Meets Selection on the Dependent Variable

I've just finished Soccernomics by journalist Simon Kuper and sports economist Stefan Szymanski. Skipping the matter of the title, I can say that the authors oversell plausible ideas and the results of multivariate regressions, seem to believe in best practice analysis, have already been shown wrong by developments that happened after the book was finished, and yet, I read its 400 pages in three days (which is very quick by my standards). It's so entertaining! But let's not give the authors too much credit. After all, what could go wrong when you pack football and econometrics into one book? It's almost as irresistible a combination as topless darts.*

An interesting factoid from the book is that only about two percent of shots from outside the eighteen-yard-box result in goals. The players are trying to score one of those spectacular "screamers" that they remember from televised matches, Kuper and Szymanski guess, and hence fall prey to the availability heuristic. But perhaps it's not simply that players remember spectacular goals better than failed attempts. Watching many live matches takes a lot of time, and matches to watch cluster on certain days, so much of football coverage is watched in the form of summary highlights of five to ten minutes. Perhaps that's especially true of professional footballers who will often themselves be at work when there are live matches to watch on the telly. And the highlights don't show all the attempts from outside the box, but they certainly show all that result in goals. In contrast, attempts from inside the box (I'm guessing) are shown at a much higher rate. Selection on the dependent variable. To be precise, that's even differential selection on the dependent variable.

On top of that, when live matches are watched, the teams that are on will often be way above average, including at converting long-distance attempts. Selection on the dependent variable again. Hence, some professional watches Gareth Bale hammer the ball into the top corner on Wednesday night and tries the same next Saturday, only to watch it sailing into the stands.

What coaches should do: Show their players a truly random sample of shots from outside the area. Ten minutes once a week should help.

*Best sentence from the link: "When L!VE TV was Millwall FC's shirt sponsor, they originally wanted to advertise this show on the shirts, but club bosses nixed that idea because they were worried it might encourage fans to throw darts." The sentence is funnier if you know a bit of context. A fine link, that one. It does not, however, mention my favourite episode "Topless Darts on the Titanic" ("Oh, no! An iceberg! Let's hope it melts before we hit it!").

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