Research
How the forecast works, in full
The 12 papers behind our Netherlands forecast (14,271 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. In het Nederlands
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12 papers · about 14k words · Our method, in short · How the elections work · Data sources
Netherlands
- Forecasting the Tweede Kamer from imperfect polls: an overview The Netherlands section forecasts the next Tweede Kamer election with the rule used for Great Britain: take half the average past miss off today's polls, but only where that would have improved past forecasts made without knowing the result. Dutch final polls, taken the day before the vote, pass that test narrowly, mostly because GroenLinks and the PvdA (now PRO) and the SP have been overstated at six of seven elections, so they are corrected. The seats follow almost directly from the national vote, and our count reproduces 2021, 2023 and 2025 exactly; who governs depends on the 76 line and on what the parties say about each other. This paper maps the other Netherlands papers.
- Measuring Dutch polling error, 2006–2025 We measure the error of the final polls at the Tweede Kamer elections from 2006 to 2025, all published the day before the vote: which polls count, how merged parties are measured, how seats-only polls are handled, the error party by party and on the gap between the two largest parties, each pollster's record and the long view. The centre-left (GroenLinks and the PvdA, now PRO) and the SP were overstated at six of seven elections; the largest misses belong to parties that rose late, the PVV in 2023 above all.
- Reading Dutch polls: the correction and its test The core methods paper for the Netherlands. Taking off half the average past miss, with each election predicted from the others, was closer on average at the seven Tweede Kamer elections since 2006, by a small margin, so Dutch polls are corrected. The gain comes from PRO and the SP, overstated at almost every election; the PVV and the VVD, whose misses change sign, are made slightly worse. We set out what the correction does to today's polls, why there is no raw-figure test and the seat count that reproduces 2021 to 2025.
- From votes to seats: the Kieswet We implement the seat count of the Tweede Kamer: one national count, a seat for every full kiesdeler (1/150 of the valid vote), and the remaining seats by highest averages among lists with a full kiesdeler. Run on the Kiesraad's official votes, the count reproduces every party's seats in 2021, 2023 and 2025. We work through 2025, explain the list combinations abolished in 2017, and say what the seat step adds: the kiesdeler cliff, the rounding and the largest party.
- Coalitions: the largest party, the 76 line and who ruled out whom Seats do not say who governs in the Netherlands. The largest party usually leads the formation, a majority needs 76, and in 2025 the combinations with 76 were blocked by what the parties had said about each other, leaving a minority cabinet with 66 seats. We give each party's chance of coming first, list every combination of two to four parties that reaches 76 in our projection with its chance of a majority, and show the statements made against each during the 2025–26 formation.
- Polls that publish only seats: deriving shares from seat headlines Dutch pollsters lead with seats, and Peil.nl publishes nothing else. The forecast works in vote shares, so a seats-only poll is read as seats ÷ 150. We explain what that loses (rounding to 0.67 points, and the votes of lists without seats handed to the rest), measure it on polls that published both (about a quarter of a point per party), and show why it matters little for the forecast.
- Simulating Dutch polling error: where the chances come from Seat ranges, the chance of each party winning a seat and of coming first, and the chance of each combination reaching 76 come from 2,000 simulated elections, each party moved by its typical final-poll miss and the Kieswet count run on the result. There is no local error, because there is one national district. Because the PVV's and the VVD's errors have often run in opposite directions, drawing them independently makes combinations containing both more uncertain than the record suggests.
- From today to polling day in the Netherlands We test the British pull-back towards the previous result on Dutch polls at ten distances up to three years before the elections of 2012 to 2025. Unlike in Italy it helps: the best curve keeps a little over half of each party's change since the last election, and it was closer than the polls at nine of ten distances. The polling-day forecast moves today's corrected shares part of the way back to 2025 and widens the ranges for the time left.
- If we're wrong: replaying past Dutch polling misses on today's polls Nine readings of today's Dutch polls: as they stand, our corrected projection, and each Tweede Kamer election's final-poll miss since 2006 replayed in full, all through the same seat count. The misses of 2017, 2021 and 2023, each with a late mover, change the largest party; none gives the parties of the Jetten cabinet a majority. We explain the count of gemeenten whose leading party changes.
- Rating Dutch pollsters: accuracy, the lead and openness Each Dutch pollster is rated out of 100 on the British scale. Verian and Ipsos I&O, which publish reports with vote shares, samples and weighting notes, are graded B; Peil.nl, as accurate as anyone at final polls but publishing seats only, is graded C. We set out the evidence, the openness items, what we could verify and why Dutch grades cannot be compared with other countries'.
- The Dutch data: results, maps, statistics, members and polls Where every number on the Dutch pages comes from: the Kiesraad's results (CC0) nationally since 1946 and by gemeente since 2012, CBS and Kadaster boundaries and CBS statistics through PDOK, the Tweede Kamer's open data, and polls from the pollsters' own reports or Wikipedia's tables. How each was changed and checked, the lineage coding, the licences, and why the Tweede Kamer's portraits are not used.
- What we don't know yet: limitations of the Dutch forecast Every known weakness of the Dutch forecast in one place: a correction that passes narrowly and rests on PRO and the SP, late movers no average can foresee, parties that merge and split, seats-only polls, three pollsters, independent errors, coalition statements that may not last, the date and the pull-back, and the map. For each, how much it matters and what would change our mind.
