Labor unions remain politically influential despite declining memberships globally.

Data & Methods:

Combining survey data of American workers with inferential techniques exploiting legal union choice variation and policy position reversals over time.

Key Findings:

Unions significantly shape members' trade preferences, but self-selection accounts for only a quarter of this effect. Workers' policy views align with unions despite ideological mismatches.

Real-World Relevance:

This study demonstrates how unions cohere workers' political voices and highlights the role of information in preference formation.