The Basque Country Votes by Where Its Neighbors Come From: The Mark of Internal Migration

In Basque municipalities with the most residents born in other regions of Spain, the PSE-EE (Basque Socialists, PSOE) and the PP post their best results. Where almost everyone was born in the Basque Country, EH Bildu and the PNV (Basque Nationalist Party) win. In 2023, among the fifth of the electorate with the most residents born elsewhere, the PSE got 33.5%. Among the fifth with the fewest, it got 13.5%, and EH Bildu 38.9%. But the Basque Country of the 1950s-to-1970s migration is aging, and the share of people born in other regions keeps falling while the share born abroad grows.

30 October 2026 · Miguel · Leer en español

A society built from two great waves

Between the 1950s and the 1970s, hundreds of thousands of people came to the Basque Country from Castile, Extremadura, Andalusia and Galicia to work in the industry of Bizkaia, Gipuzkoa and Álava. Half a century later, their children and grandchildren were born in the Basque Country. The first generation remains a visible part of the population. Over the last two decades a second wave has arrived, this time from abroad.

According to the municipal population register of Eustat (the Basque statistics institute), in 2023 the Basque Country’s residents were distributed as follows:

• Álava: 64% of residents were born in the Basque Country, 21% in another region and 15% abroad.
• Gipuzkoa: 74%, 14% and 12%.
• Bizkaia: 71%, 17% and 12%.

The two curves cross. The share of people born in other regions has fallen in all three provinces since 2008, because that generation is aging and dying. The share born abroad is rising, reaching 14% to 16% in 2025. In Gipuzkoa there are now almost as many residents born outside Spain as in other regions (13.8% versus 13.2%).

The vote follows that line

We matched each municipality’s population register with its results in the 2008 to 2023 general elections. We then sorted the electorate into five equal-sized groups (quintiles) by the percentage of residents born in another region:

• Where almost everyone was born in the Basque Country (first quintile, with 8.6% born in another region), EH Bildu got 38.9% and the PNV 32.6%. The PSE-EE stayed at 13.5% and the PP at 4.6%. These are mainly the towns and villages of inland Gipuzkoa, Bizkaia and northern Álava: 156 municipalities.
• Where the most residents were born elsewhere (fifth quintile, with 22.8%), the order flips. The PSE-EE got 33.5%, the PNV 16.8%, EH Bildu 15.9% and the PP 15.5%. These are the large industrial municipalities on the left bank of the Nervión estuary, Vitoria-Gasteiz and its surroundings: only 22 municipalities, but as many voters as the other 156.

The relationship is very strong and has been stable since 2008. In every election, the correlation between the share born in another region and the PSE-EE vote is between +0.86 and +0.90, and for EH Bildu between −0.72 and −0.75. The PNV’s is also negative in every election: between −0.70 and −0.74, except in 2011 (−0.54). The PP, Vox and Podemos or Sumar also do better in municipalities with more residents born outside the Basque Country. With those born abroad the relationship is much weaker: most do not hold Spanish nationality and cannot vote in general elections.

What these data do not say

• They do not say how each person votes. That municipalities with more internal migration vote more for the PSE does not mean that those born elsewhere vote PSE and those born in the Basque Country vote Bildu or PNV. Many children of that migration vote for nationalist parties, and many Basques of several generations vote PSE or PP. This is an ecological analysis: it describes where each origin group lives and how those municipalities vote.
• Origin is mixed up with other things. Municipalities with internal migration are also the most urban, industrial and Spanish-speaking. Origin cannot be separated from language, size or working-class history.
• Individual-level data are missing. No recent CIS survey asks about place of birth in a way that allows analysis of the Basque Country. Only the 2016 post-election survey does, and it has fewer than 300 interviews in the Basque Country. A Basque survey with that question would make it possible to separate origin, language and vote.

What it could mean for 29N

If the PSE-EE’s base lies in municipalities of internal migration and that generation shrinks, its most loyal electorate shrinks over time. Meanwhile, EH Bildu dominates where the population is more native-born. This is only an underlying trend, which shifts from election to election, not a forecast. But it helps explain why the Basque Government’s Sociómetro, published today, gives EH Bildu seven seats and the PNV four. Our model gives Bildu six, the PNV and the PSE five each and the PP two. The difference is one seat in Bizkaia.

How we calculated it

• Population. Eustat municipal population register (population table by place of birth), January 1 of each election year: born in the Basque Autonomous Community, in other provinces of Spain and abroad (pv_origen.py). Navarre is excluded: there is no comparable municipal series before 2021.
• Vote. Polling-station results from the 2008 to 2023 general elections (Ministry of the Interior), summed by municipality, excluding the overseas vote. EH Bildu includes Amaiur in 2011. In 2008 the Basque pro-independence left had no legal candidacy; Eusko Alkartasuna and Aralar, which did, appear under “others”.
• Quintiles. Municipalities sorted by the percentage born in another region and grouped into five groups with the same number of valid votes.
• Code. pv_origen.py and articulo_pv_origen.py, in the altnalysis repository.