Support for the Major German Parties, Estimates and Predictions (Week 35, 2013)
Exactly three weeks before the 18th Bundestag election, it’s time for another look at the polls. This weekend brings six new entries: One late result from week 33 that was only published a week ago, three polls from week 34, and two that were conducted this week, with fieldwork done from Monday/Tuesday to Wednesday. For all purposes and intents, that means that any possible fallout from the Western (non-)intervention in Syria will not be reflected in the polls.
Raw Figures, Estimates and Predictions
As always, there is a good deal of variation in the published figures. The range for Merkel’s Christian Democratcs, for example, is 41 to 46 per cent. But for what it is worth, the model is ever more confident about the outcome of the election: The estimated probability of victory for the governing coalition is now 85 per cent (up from 78 per cent) even if one ignores tactical voting by CDU supporters. If this “loan vote” is factored in, the probability of a coalition victory is 94 per cent (up from 90). Unsurprisingly, the probability of a Red-Green majority is still estimated as zero.
Support for the Minor German Parties, Estimates and Predictions (Week 35, 2013)
The one remarkable change is the modest slump in support for the Greens, which have lost about two points over the last four weeks and are now well below their peak support of about 15 per cent in March. The slow upward trend of the Liberals is unbroken, and the Left is safely above the electoral threshold. Support for the two major parties is perfectly stable.
Since my interest here is (mostly) academic, I also began comparing past predictions (from week 33) with current estimates. The differences are small, but there is one interesting exception: Support for the Greens is now estimated to be 0.8 points lower than it should have been, given the information that was available two weeks ago. So it would seem that their support is indeed suffering from some random shock.
Today is the day of the televised debate between Steinbrück and Merkel (in Germany, known as “the Duel”). While we are professionally obliged to watch it, I don’t think that it will make much of a difference. Both candidates are extremely well known knowns. I also don’t think that Syria will matter for this campaign.
Have I just shot myself in the foot? Probably. Come back next week for the latest batch of surveys.
It is still silly campaign season in Germany, and the new exhibits just keep coming. Here is another one brought to you by the Party Formerly Known As The Guys Who Almost Stood Up Against The Bloody Spelling Reform Back In The 1990s.
Incidentally, the party also upset a lot of German teachers back in 1968 when they began styling their logo as F.D.P. (a violation of clause 102, subsection 2 of the German spelling code). They shed the dots back in 2001, when a youngish Guido Westerwelle took over and transformed the party. So possibly, just possibly, Regained. Full. Stops. Between. Buzzwords. Are. The. Message.
Here is another gem from my ever growing collection of slightly leftfield campaign posters. While the world is debating Syria, the local CDU chapter and their supporters take a walk to discover local Nutzkräuter (really useful herbs) and Wildkräuter (wild herbs, which must be potentially useful too?). The long-suffering candidate will tag along. Seriously. I bet all this weed is going to tilt the electoral balance.
As an aside, note that all local CDU poster refer to “our” (unser) candidate, presumably because nobody ’round here knows the poor man.
everyThe Free Dictionary: Constituting each and all members of a group without exception. →
On average, polls are in the field for five days (with a standard deviation of three days), so I continue to anchor each poll to a specific week in the calendar. Along with the raw data, the graphs show estimates for the true support for each party over 32 weeks, starting from Monday, the 31st of December. Eight of the new polls cover week 31 and week 32, while one is a late addition to estimate for week 30.
Estimated/predicted Support for Major German Parties (2013 election). Click for Larger Image.
Support for Merkel’s Christian Democrats is between 39 and 47 per cent. The model, which accounts for previous levels of party support and variation across pollsters, puts them at 41 per cent. Findings for the major opposition party, the Social Democrats, are less variable at 22 to 25 per cent. The model places them at the upper limit of these current polls.
Results for the Greens are even more unanimous (12-13.5 per cent). The model agrees, confirming that their support has come down a tick or two over the last weeks.
The same cannot be said for the Left, which is almost static at seven per cent (polls: 6-8.1). That is well below their 2009 result, but also well above the electoral threshold of five per cent.
Finally, for the Liberals, Merkel’s coalition partner, things have improved ever so slightly. While the polls vary from three to seven per cent, the Liberals’ true level of support is currently estimated at 5.2 per cent. More importantly, after months of continuous near-death experiences, there seems to be an upward trend.
Estimated/predicted Support for Smaller German Parties (2013 election). Click for Larger Image.
What Does That Mean for September 22 and Beyond?
This is my first shot at pooling the pre-election polls, so all predictions should be taken with a very generous pinch of salt. The model is possibly misspecified and rests on an number of questionable assumptions. The most obviously problematic amongst these is that polls are, on average, unbiased over the whole January-September timeframe. But hey, this is a blog, so let’s ignore this (and all other) problems for a second and believe that the trend-lines and credible intervals for the next four weeks are indeed credible.
Once we make this leap of faith, the probability of a return to a Red-Green coalition is approximately zero. Amongst 10000 simulations of week 38/39 (the election is on a Sunday), there is not a single one that gives a parliamentary majority to this prospective coalition.
The FDP, on the other hand, makes it past the electoral threshold in 83 per cent of my simulations, and in 78 per cent, there is a parliamentary majority for the present coalition. The true probability will be higher, as some CDU supporters will vote strategically for the FDP to help them across the threshold. If we assume that this behaviour is virtually guaranteed to succeed (it would be enough if about one in 40 CDU would cast a “loan vote”), the probability of a majority for the present coalition goes up to 90 per cent.
Put differently, the probability of a Red-Red-Green coalition (SPD, Left, Greens) is between 22 per cent (no loan votes for FDP) and 10 per cent (loan vote strategy works perfectly). But even if there was a majority for the three opposition parties, a coalition (or rather a toleration arrangement with the Left) would be highly unlikely (say p=0.1), making a Grand Coalition led by the CDU the default option. That again means that the probability of any government not being headed by the present chancellor is between one and two per cent (down from four per cent last week).
What About the Smaller Parties (AfD, Pirates, etc.)
For several months, most pollsters did not publish separate results for smaller parties such as the eurosceptic AfD or the internet-centric Pirates. Some have resumed giving itemized counts for “other” parties, and it currently seems safe to assume that neither will enter parliament. If they did, the Pirates would probably take away votes from the left parties, whereas the AfD would most likely weaken the two major parties. In either case, a Grand Coalition would become more likely.
This post comes with lots of health warnings attached. In the past, forecasts have failed, faces have turned red, majorities have collapsed well before election day. I’ll be back once I have collected the next batch of polls.
Just over five weeks before the Bundestag election, there is much merriment about the current state of play. Support for the Liberals has been consistently below the electoral threshold of five per cent for months, which implies that Merkel’s coalition would not be able to continue after September. Consequently, everyone is very excited about a more recent series of polls, which put the party at exactly five per cent. But even with n=2000, an exact confidence interval would range from 4 to 6 per cent. Add multistage sampling, house effects, and the fact that people do not necessarily know how they will vote in September, and you end up with a lot of noise.
Support for the Two Major German Parties in 2013
How much noise exactly? The good folks at wahlrecht.de publish marginal distributions for six major companies that regularly conduct random polls. I wrote a little program to collects everything published since January (the exact election date was officially determined on February 8 but was negotiated between the parties in January). Here are the results (click to enlarge).
Most polls are in the field for two to seven days, so I anchored them at their midpoints. My current data set spans 31 weeks, with just under 4 polls conducted each week.
Polling the German Election Polls
It’s obvious that there is a lot of variation in these 120 data points, making claims that this party has declined while another one surges rather dubious (though they still make excellent headlines). Poll aggregation is one possible and increasingly way out of this conundrum, so I decided to get my hands dirty, install (r)jags and bite the Bayesian bullet (something I have meant to do for years).
Support for three of the Smaller German Parties (2013)
My model is rather simplistic (I’ll post the code once it has stabilised). I assume that reported voting intentions are distributed multinomial, and that they depend on a) latent party support and b) house effects. I further make the rather heroic assumption that house effects are random with a mean of zero. Latent party support, on the other hand, follows a random walk, possibly with a drift: This week’s support is last week’s support plus some random change due to political events, plus some constant that accounts for steady up- or downward trends.
The Bayesian framework seems particularly appropriate here as it is technically and conceptually easy to come up with predictions for September 22, but I refrain from incorporating any prior beliefs and put vague distributions on all parameters. As far as I can tell (and that does not mean a lot), the model seems to converge without problems.
Estimated and Predicted Support for Major German Parties (2013)
Somewhat surprisingly,the 95 per cent credibility interval (the shaded area around the trend line) is rather narrow for both the CDU and the SPD, implying that we can learn a lot from pooling many noisy polls. Support for Merkel’s Christian democrats was largely stable over the last seven months at about 42 per cent. This would make them the strongest party by far, although they are far away from the lofty 50 per cent they reached in some polls in April and June. According to the model, support for the Socialdemocrats is similarly stable, though at a much lower level of 26 per cent.
The predictions (to the right of the vertical line that marks the beginning of the last week included in the model) are less precise than the estimates, and become more vague as they extend towards election day, but it seems almost certain that the CDU will be the strongest party in the new parliament by a fair margin.
Estimated and Predicted Support for Smaller Parties in Germany (2013)
The model is also very confident about levels of support for the smaller parties. Green support peaked in March, but current and predicted levels are still above 12 per cent, which would be an improvement on the 2009 result. But since the SPD is so weak, the probability of a “Red-Green” majority in the next Bundestag is estimated to be (much) less than one per cent.
Support for the Left is estimated at about seven per cent, well above the threshold (the dashed line), but also well below their very strong result in 2009.
Finally, the FDP has shown an upward trend over the last 10 weeks or so and is projected to cross the threshold just in time for the election. The model estimates the probability of the FDP returning to parliament at 67 per cent.
Predicting the Inevitable
In reality, a sufficient number of potentially CDU voters might support the FDP for tactical reasons, pushing up that number towards certainty. But the coalition could come to an end even if that manoeuvre succeeds: The odds that the coalition garners more votes than the three left parties together are only slightly better than even at 58 per cent.
A “Red-Red-Green” coalition (or rather a Red-Green government tolerated by the Left), however, seems politically infeasible, suggesting a return to a Great Coalition lead by Angela M. with a subjective probability of at least 90 per cent.
If (if!) I take these estimates seriously for just one moment, that means that probability of Ms Merkel retaining her office is roughly 96 per cent. Let’s see how the next batch of polls plays havoc with this figure, shall we?
Trying to Rub off the Incumbency Advantage from the Old Guy
The local MP is stepping down after a mere 19 years, and the local mayor wants his job. The outgoing MP won his seat five times in a row on a plurality of the Erststimmen. Structural factors aside, this looks like an incumbency advantage (though the 2009 result was rather close).
Can he pass this on to the successor? In the 2010 UK General Election, party incumbency (as opposed to personal incumbency) did not make a difference for new candidates. I’m not sure if it will play in the 2013 election over here, but I doubt that this poster will help.