All parliamentary data is sourced directly from official institutions. Each entry refers back to the original publication or dataset, and is reused under the license or terms of use shown with it.
Seat counts are compiled by this site from the data of the institutions credited; they are not an official publication of those institutions. The date each chamber's seats were last updated is shown with its chart and on the status page.
Rovny, Jan, Ryan Bakker, Liesbet Hooghe, Seth Jolly, Gary Marks, Jonathan Polk, Marco Steenbergen, and Milada Vachudova. “25 Years of Political Party Positions in Europe: The Chapel Hill Expert Survey, 1999-2024,” working paper.
Open data portal of the Spanish Congress of Deputies. Seat counts are aggregated from the "DiputadosActivos" export, grouped by its GRUPOPARLAMENTARIO field.
Datan's "Groupes politiques actifs de l'Assemblée nationale" dataset, published on data.gouv.fr, listing every active political group of the French National Assembly with its current membership.
Parline, the Inter-Parliamentary Union's open database on national parliaments, covering chamber composition, electoral systems and parliamentary procedure.
Open data of the Austrian Parliament, "Parlamentarier:innen ab 1918" dataset. Seat counts are aggregated from the members holding an active mandate in each chamber, grouped by the club (Klub) or Fraktion of that mandate.
Herrmann, M. & Doring, H. (2023). Party Positions from Wikipedia Classifications of Party Ideology. Political Analysis, 31(1), 22-41. doi:10.1017/pan.2021.28. Data: Doring, H. & Herrmann, M. Party Positions from Wikipedia Tags. doi:10.5281/zenodo.7043510. https://github.com/hdigital/partypositions-wikitags
Public API of the French Senate listing every sitting senator with their political group (groupe.code / groupe.libelle). Seat counts are aggregated per group.
Official OData API of the Swiss Federal Assembly, published by the Parliamentary Services. Seat counts come from the MemberCouncil entity: the active members of each council, grouped by parliamentary group.
Rooduijn, M., Van Kessel, S., Froio, C., Pirro, A., De Lange, S., Halikiopoulou, D., Lewis, P., Mudde, C. & Taggart, P. (2023). The PopuList 4.0: A Database of Populist, Far-Left, and Far-Right Parties Using Expert-Informed Qualitative Comparative Classification (EiQCC). OSF. https://doi.org/10.17605/OSF.IO/2EWKQ. Covers national elections from 1 January 1989 to 1 May 2026.