Madrid accounts for 14.5% of Spain’s population but receives 10.9% of the seats in Congress. The 3.6-point gap is the widest among the provinces. Separately, Spain’s National Statistics Institute (INE) published its third-quarter 2026 Labour Force Survey on 27 October, with provincial results; it recorded a quarterly decline of 49,200 employed people in the Community of Madrid.
A population-driven redistribution assigns Madrid 38 seats, one more than before, while Cádiz loses one. Madrid gains representation in absolute terms, but the gap between its share of the population and its share of the chamber remains.
The difference is stark at constituency level. Each Madrid MP represents 188,655 residents. In Soria or Teruel, the ratio is just over 45,000.
Barcelona is the next most underrepresented province: it accounts for 12.1% of Spain’s population and 9.1% of Congress, a 3.0-point gap. Valencia and Alicante are also more underrepresented than Cádiz, whose 2.6% population share compares with 2.3% of the chamber. Seville and Málaga rank above Cádiz, as do Murcia and the Balearic Islands.
The seat system helps explain the imbalance. Congress has 350 seats. Every province receives two regardless of population, while Ceuta and Melilla each receive one. The remaining 248 seats are distributed according to population, so demographic changes can shift provincial allocations.
Several provinces have a larger share of seats than of Spain’s population. Salamanca and La Rioja are among them, as are Lugo and Zamora. Orense and Ávila also fall into that group, along with Segovia, Palencia and Teruel.
Madrid has gained six seats since the 1977 democratic elections, when it began with 32. That is the largest increase of any province. Málaga and Alicante also gained seats, as did the Balearic Islands. Yet the population-to-seat gap has widened from 3.0 points in 1977 to 3.6 points in the allocation described.
Barcelona began with 33 seats and has 32. Asturias has lost three since 1977 and now has seven, leaving it slightly underrepresented. Vizcaya and León have each lost two seats, as have Badajoz and Jaén. Vizcaya is slightly underrepresented; León and Badajoz are overrepresented, as is Jaén.
International assessments identify constituency design as the weakest measure of Spain’s electoral system. The benchmark study Percepciones de la Integridad Electoral (PEI, por sus siglas en inglés), led by researchers at the Universidad de Harvard, gives Spanish constituencies 59 points out of 100, the lowest score among its indicators. The PEI’s latest assessment of Spain covers the 2023 general election.
The same study scores vote counting above 90. Election procedures and the work of electoral authorities also receive marks above 90. Preparation of the electoral register earns 93. The assessment predates disruption linked to the ley de nietos in overseas voting.
The PEI points to the higher number of votes needed to secure a seat in heavily populated provinces than in smaller ones. This disadvantages medium-sized national parties compared with larger parties, as well as regional groups that concentrate their support. The source cites Izquierda Unida historically and Vox in recent elections among those affected. Basque and Catalan nationalists have benefited. Separate coverage of Madrid’s Congress candidate lists examined the positions held by three mayors.
