Blais, A. Fr Polit (2016) 14: 126. doi:10.1057/fp.2015.24
I show that, contrary to Duverger’s law, three or four parties receive at least 5 per cent of the votes in most districts in British and Canadian elections. This is so because the voters and the parties are not necessarily short-term utility maximizers as the theory assumes. Still, the basic intuition that fewer parties obtain significant support under single-member district plurality elections is absolutely correct. Duverger also makes an important contribution instressing the impact of electoral formulas, a fruitful antidote to the exclusive emphasis that recent research has given to district magnitude.
Duverger electoral formula district magnitude plurality electoral system