Nov 252013
 

The very useful OUP blog has a Q&A session on polling accuracy with Jocelyn Evans and me: Polling accuracy: a Q&A with Kai Arzheimer and Joceyln Evans.

Moreover, Oxford University Press has kindly ungated the Political Analysis paper on our New Multinomial Accuracy Measure (TM), so grab the PDF while it is free.

Sep 012013
 

The Polls

majorparties-week-35

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.

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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.

The Outlook

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.

Aug 242013
 

The State of Play, Four Weeks Before the Election

Last week’s post on Merkel’s very good chances to win a third term created a bit of a stir. This week, I’m back with nine new polls (conducted between August 6 and August 19 by six different companies), which all point into the same direction.

What the Pollster Saw

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.

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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.

minorparties-week-33

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.

What Everyone Else Thinks

The July issue of PS has two short pieces on forecasting models for the September election. Both pick Merkel as winner. So do Bundewahltrend (average over the six most recent polls), pollytix (weighted average of 15 most recent polls), and wahlistik (a poll aggregator run for the Zeit weekly). Las weekend, politicians in both major parties began floating the idea of a Grand Coalition, but given the latest polls, four more years of centre-right government seems to be the most likely option by far.

Stay Tuned

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.

Jun 232013
 

All surveys deviate from the true distributions of the variables, but some more so than others. This is particularly relevant in the context of election studies, where the true distribution of the vote is revealed on election night. Wouldn’t it be nice if one could quantify the bias exhibited by pollster X in their pre-election survey(s), with one single number? Heck, you could even model bias in polls, using RHS variables such as time to election, sample size or sponsor of the survey, coming up with an estimate of the infamous “house effect”,.

Jocelyn Evans and I have developed a method for calculating such a figure by extending Martin, Kennedy and Traugott’s measure A to the multi-party case. Being the very creative chaps we are, we call this new statistic [drumroll] B. We also derive a weighted version of this measure B_w, and statistics to measure bias in favour/against any single party (A'). Of course, our measures can be applied to the sampling of any categorical variable whose distribution is known.

We fully develop all these goodies (and illustrate their usefulness by analysing bias in French pre-election polls) in a paper that
(to our immense satisfaction) has just been accepted for publication in Political Analysis (replication files to follow).

Our module survebias is a Stata ado file that implements these methods. It should become available from SSC over the summer, giving you convenient access to the new methods. I’ll keep you posted.