Physics challenges the optimal size of parliaments

(Image: Pixabay CC0) - Analyzing a classic paper that has influenced the size of parliaments for almost half a century, an EPFL physicist discovers major flaws with its methodology, challenges its fundamental assumptions, and calls for a complete and careful re-think of its government-governing rule. What is the best size of a parliament? That is a question at the center of many countries today, including the 2020 referendum in Italy where almost 70% of voters selected to slash the number of members of parliament by about a third. Among others, the complex issue involves matters of governing efficiency, logistics, and financial costs. But one thing many people might not realize is that there is a science behind all this. In 1972, political scientist Rein Taagepera published a seminal paper proposing that the ideal size of a parliament corresponds to the cube root of the country's population: A=αP_o^1/3 , where A is the parliament size, P_o is the population size, and α is a constant. In general terms, the bigger a country's population, the bigger its parliament ought to be. Taagepera's famous -cube-root law- was quickly taken up by governments, but hasn-t been without critics: In 2007 and 2012, researchers used empirical data to come up with a square-root relationship rather than a cube-root, while another paper in 2019 questioned the actual cause-effect sequence that lies at the foundation of Taagepera's law.