Beyond Left–Right: Europe’s Parties Split Across Multiple, Cross-Cutting Divides

Why Multidimensional Polarization Matters

Jelle Koedam, Garret Binding, and Marco R. Steenbergen tackle a core puzzle about contemporary party competition in Europe: while scholars increasingly recognize multiple ideological divides (economic, cultural, etc.), measurement of party polarization still often treats politics as one-dimensional. This mismatch matters because whether different divides reinforce each other or cut across one another shapes how parties compete, how voters sort, and how democratic representation functions.

How Effective Dimensionality Is Measured

The authors introduce a novel, multidimensional approach that moves beyond counting issue dimensions to assessing how those dimensions relate in practice. Their key innovation is an "effective dimensionality" measure derived from the correlation matrix of parties’ policy positions. This metric captures whether distinct ideological axes are tightly aligned (reinforcing polarization) or largely independent and cross-cutting.

Tests with Simulated and Real Data

• The method is illustrated with artificial (simulated) data to show how effective dimensionality behaves under known configurations of party positions.
• Empirical tests use positional estimates from the Chapel Hill Expert Survey (CHES) covering 1999–2019 to analyze patterns across European party systems.

What the Authors Find

• Effective dimensionality provides a clearer picture of how different ideological divides interact than one-dimensional measures.
• This approach better links party-level polarization to patterns of mass partisanship, indicating when elite divides are likely to translate into distinct voter alignments and when they remain fragmented across issues.

Implications for Polarization Research and Representation

The paper offers theoretical, methodological, and empirical contributions: it reframes polarization as a property of interrelated dimensions rather than a single axis; supplies a metric researchers can apply to cross-national party data; and changes expectations about when elite polarization will produce cohesive mass polarization. The authors’ approach sharpens tools for diagnosing whether political systems face reinforcing polarization or cross-cutting cleavages that may moderate conflict.