Party Systems Predict Regime Shifts: Introducing the Party‑System Democracy Index

Why Party Systems Matter for Democracy

Fabio Angiolillo asks a simple but consequential question: how (anti-)democratic are party systems themselves? Rather than treating autocratization mainly as an executive-led process or focusing only on opposition resistance, this study foregrounds parties’ collective regime preferences—how much disagreement about democracy versus authoritarianism exists across a country’s party system—and shows why that internal distribution matters for regime outcomes.

What the Party‑System Democracy Index Measures

The paper introduces the Party‑System Democracy Index (PSDI), a new cross‑national measure that tracks parties’ regime preferences over time. The PSDI captures the prevalence of pro‑democratic versus anti‑democratic positions within party systems, complementing traditional party‑system measures that emphasize policy differences rather than regime orientation.

How the Index Was Built and Tested

• The PSDI covers 1970–2019 for 178 countries and 3,151 country‑years.
• Angiolillo uses established validation strategies—content validity, convergent validity, and construct validity—to assess the index’s reliability and to show it maps onto related concepts in sensible ways.

Key Findings

• The PSDI is an important predictor of regime change in both directions: shifts toward autocratization and shifts back toward democracy.
• Changes in the PSDI often precede regime transitions, indicating that growing anti‑ or pro‑democratic alignment within party systems can signal a looming change in regime type.

What This Means for Research and Practice

By putting parties’ regime positions at the center of analysis, the PSDI offers a new tool for scholars and analysts interested in the roots of democratic backsliding and democratization. The index expands the party‑systems literature and provides a practical early‑warning indicator for observers tracking risks of autocratization and democratic recovery across countries.