Research
How the forecast works, in full
The 10 papers behind our Germany forecast (29,202 words): how far the polls have missed, how we correct them, the seat model and the tests.
These papers set out every part of our method: what we measure, how we correct the polls, how votes become seats, how uncertain the result is, and what we have tested and rejected. Figures marked Live are computed from the database each time the page is built, so they always match the forecast. Auf Deutsch
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10 papers · about 29k words · Our method, in short · How the elections work · Data sources
Germany
- Forecasting the Bundestag: an overview German final polls have missed by about a point per party at the six Bundestag elections since 2005, but the direction of the miss changes from one election to the next, so correcting for it would have made our forecast worse and our projection takes the polls as published. What decides the seats is the 5% line and the 2023 seat law, under which a Wahlkreis winner sits only if the party's list vote covers them. This paper sets out what the Germany section forecasts, how each step works, where the uncertainty lies, and how the other Germany papers fit together.
- Measuring German polling error, 2005–2025 At the six Bundestag elections from 2005 to 2025, the average of the final polls missed each party by about one point, except in 2005, when every pollster had the CDU/CSU about six points too high. Since then no party has been missed the same way every time, and the AfD, understated in 2013 and 2017, has been polled almost exactly at the last two elections. We define the error, describe the 52 final polls and how they were sourced and graded, and report the gap between the two largest parties, each pollster's record, earlier elections back to 1953 and the state elections held since 2025.
- How we read German polls: the 5% line and the 2023 seat law German final polls have missed by about a point per party since 2005 but never in a steady direction, and correcting them would have made the forecast worse, so we take them as they are. The seats turn on the 5% threshold and on the 2023 seat law, which our calculation reproduces exactly for 2025.
- From votes to seats: the Bundestag seat law We implement the Bundestag seat allocation under the 2023 electoral law as modified by the Constitutional Court on 30 July 2024: the 5% threshold with the three-Wahlkreis and minority exceptions, 630 seats by Sainte-Laguë/Schepers, Land lists, and Wahlkreis winners seated in order of Erststimmen share until the party's Land seats run out. Given the official 2025 votes, the calculation reproduces every party's seats, all 81 Land lists and the seated or unseated status of all 299 Wahlkreis winners exactly. National polls reach the Länder and Wahlkreise by proportional swing from 2025, a projection that has not yet been backtested.
- Simulating German polling error: where the chances come from The German seat ranges, the chance of each party entering the Bundestag and the chance of each coalition holding a majority come from 2,000 simulated elections, each moving every party's national share by a random error the size of its past final-poll miss (at least one point), adding local noise in every Wahlkreis and running the full seat law. Unlike the British simulation, errors are drawn independently for each party, which keeps every party's own uncertainty but ignores how parties' errors move together. The most important output is the chance of clearing 5%, because that single event moves dozens of seats.
- From today to polling day in Germany The next Bundestag election is due by 25 March 2029, so today's polls are not a forecast of polling day. Testing the British pull-back towards each party's last result on polls at ten distances before the five elections from 2009 to 2025, we found it made German forecasts worse at every distance, because change between Bundestag elections has been large and has mostly lasted. The polling-day forecast therefore keeps today's shares and widens the uncertainty with the time left, by a curve fitted to how far polls have missed at each distance.
- If we're wrong: replaying past Bundestag polling misses on today's polls We apply each Bundestag election's final-poll miss from 2002 on (the model uses no election before 2000) to today's German poll average and run every reading through the same seat engine. German misses are modest, but the 5% line turns them into jumps: a replay that lifts a small party over the threshold hands it thirty or more seats and changes which coalitions add up. The same replays change the Erststimme winner in some Wahlkreise, which the map and seat pages mark as at risk; under the 2023 law that changes who sits, not how many seats each party gets.
- Rating German pollsters: accuracy, the lead and openness We score each German pollster out of 100 on its final Bundestag polls since 2005, shrunk towards a poor pollster, on its error on the gap between the top two parties, and on what it publishes. Because German final polls have been more accurate than British ones, the same scale gives German pollsters higher grades, so the order matters more than the letters. Forschungsgruppe Wahlen's raw Stimmung was further from the result than its own Projektion at five of six elections, which is why, unlike in Britain, we do not start from raw figures.
- The German data: results, boundaries, polls and licences Results, Wahlkreis boundaries, Strukturdaten and members come from the Bundeswahlleiterin under the Datenlizenz Deutschland and were checked 24 ways before use. Polls come from pollsters' own releases where they publish a readable series and otherwise from Wikipedia, graded C and marked; 405 of the 508 German polls are grade C. New polls are found by a daily check of three pollsters' pages and entered by hand or CSV, with validation before anything is stored; no aggregator's data is used.
- What we don't know yet: limitations of the German forecast The German forecast rests on six Bundestag elections, with 2005 dominating the averages and the simulation's spread. Its uncertainty is concentrated at the 5% line, where independent party errors and an interim three-Wahlkreis rule are simplifications; it has one election of history for the BSW, an untested proportional swing with no candidates, too few regional polls, an uncertain election date and mostly second-hand polls. For each we say how much it matters and what evidence would change our mind.
