Case studies on PR vs FPTP: turnout, polarization, and isolating system effects

[Donald_L]

I'm a political science student researching the impact of different electoral systems on voter turnout and political polarization, specifically comparing proportional representation to first-past-the-post models. My hypothesis is that systems which produce more representative legislatures see higher long-term engagement but also potentially foster niche, extremist parties. For academics or policymakers who have studied this, what real-world case studies or election data sets most clearly demonstrate the causal relationship between the voting mechanism and these societal outcomes, and how do you isolate the effect of the electoral system from other factors like political culture or media landscape in your analysis?