🔬 How counterfactual representation is simulated

This approach uses multilevel modeling and post-stratification to estimate how legislative outcomes would change under alternative representation rules. The method can simulate scenarios that, for example, boost the share of women in a legislature or change how votes translate into seats.

📊 How outcomes are estimated

• Multilevel modeling and post-stratification (MRP/post-strat) are combined to produce estimates of legislators’ preferences and roll-call outcomes under different representation rules.
• Counterfactual schemes considered include altering the demographic composition of delegations and converting votes into seats by party-proportional rules.

📌 Applied questions

The technique is applied to two illustrative questions:

• Would the U.S. Congress be less polarized if state delegations were formed according to the principle of party proportional representation?
• Would there have been stronger support for legalizing same-sex marriage in the U.K. House of Commons if Parliament more closely reflected the population in gender and age?

💡 Why this matters

• Provides a practical toolkit for estimating the legislative consequences of alternative representation designs without needing real-world reform.
• Enables direct comparison of institutional changes (seat allocation rules) and descriptive representation changes (gender and age composition) on policy-related outcomes.

📎 What readers can expect

• A clear description of the modeling and post-stratification workflow used to generate counterfactual legislatures.
• Concrete applications showing how the method addresses questions about polarization and substantive representation in two well-known democracies.