Economics
How Electoral System Design Shapes Party Fragmentation
Quick fact
In countries using winner-take-all districts, such as the United States, the effective number of parties is nearly always around two, while proportional systems often produce three or more significant parties—sometimes as many as six or seven in the legislature.
Why this is interesting
Why do some countries have two dominant political parties, while others have many parties that must form coalitions? The answer lies not just in voters but in the rules of the election game itself.