Catalonia’s pro-independence parties won a major victory Thursday: Together, they secured a five-seat majority over all other parties in the Catalan Parliament. Separatists were triumphant about their victory. But here’s the problem: The separatist victory is a manufactured product of Catalonia’s electoral system, in which voters cast their ballots for a single party list and seats are awarded to parties proportionally using the d’Hondt formula within each of Catalonia’s four provinces. As I’ve explained before, this system is stacked in favor of the separatists — which is how the three pro-independence parties won a parliamentary majority while receiving just 47.7 percent of the vote. Three factors skewed the results. First, Catalonia gives the three more rural provinces, where separatist parties do well, 15 more of the 135 total deputies than they merit based on population. Conversely, Barcelona, the most unionist province, is underrepresented. This is known as “malapportionment.” Had Catalonia allotted seats fairly among the provinces, pro-independence parties would have fallen one seat short of a majority.
Second, separatist parties benefit from the tendency of districts with fewer seats to give a bonus to stronger parties. The disproportionality between the share of votes and seats won by a party increases as the number of seats declines.
In a district with just one seat — like in the U.S. House — it’s possible to win with just 51 percent (or sometimes less) of the vote. The same thing is true even under proportional representation. In districts with just a few seats, you sometimes see similar disproportionality. In 2016, Spain’s governing People’s Party won two of the three seats in Cuenca province with just 46 percent of the vote.
Had Catalonia held its elections in a single, regionwide district, separatist parties would have won just 66 seats — two short of a majority.