It’s just a single poll
Once more, repeat after me: It’s just a single poll. It’s also the time for horse-race journalism (and for horse-race blogging). In this specific case, the single poll is the most recent instalment of the “Deutschlandtrend”, a survey-series that Infratest-dimap runs for public broadcasting giant ARD. From the results (SPD: 20, AfD: 12), Focus Online has created a lovely headline: SPD in freefall, AfD at highest level of support in seven months. But is there really a story?
Now for the horse-race blogging. Since my last blog (day before yesterday), three new polls have been published. Why bother to start the big and mysterious poll-pooling machine again? Because I can, because in a week or so, there will be no new polls, and because I want to see if there is anything to the Focus story.
First, a closer look at the Infratest-dimap poll, which is clearly the most recent piece of information: field time was only the last two days (September 12-13), and it was published immediately. The other two “new” polls are not really that new. They were in the field from September 8-11 (Insa) and September 4-8 (Forsa) and put the SPD at about 23 per cent and the AfD between 9 and 11 per cent for these slightly earlier time spans. Does that suggest some dramatic movement during the last couple of days? Not really. Infratest-dimap tends to produce somewhat low-ish estimates for the SPD, and rather high estimates for the AfD. The (estimated) house effects are -0.7 and +1.7 points, respectively. The house effects are not calibrated in any way, so Infratest-dimap’s estimates may be perfectly correct, but across all the polls in the model, their estimates for these two parties tend to be below/above average. This is neatly illustrated in the graph:
All Infratest-dimap polls (the hollow circles) put the AfD well above the model-based credible interval, and this one (the rightmost circle) is particularly far away from the envelope. The current credible interval for the AfD is 8.6-10.3%. The AfD’s mini-upward trend may be real, but this poll is probably exaggerating the development.
Infratest-dimap may also underestimate support for the SPD. The model currently puts the SPD between 21.4% and 23.6%. The Infratest-dimap poll (rightmost filled red circle) is well below the credible interval. Things don’t look great, but it’s not “freefall”. The credible interval for the gap between the the SPD and the AfD is 11.6-14.6 points, so the 8 point gap reported by Focus on the basis of a single poll looks like a bit of an over-dramatisation. The AfD is not (yet) catching up with the Social Democrats.
Will the AfD be Germany’s third party? In the model-based simulations, their chances have gone up from 18% to 39%, but that is still far from certain.In actual fact, according to the model, the Left has a better chance (50%) to become the largest of the minor parties. But that would be a far less dramatic story. And realistically, this is all by the by: the four minor parties enjoy virtually identical levels of support.
Coalition options are the same as they were three days ago. So what is the bottom line? This last poll (and the other two) make good headlines, but in terms of likely politically relevant outcomes, the situation has not changed at all.
Also published on Medium.