Legislative Political Environments and Policy Outcomes

Who really makes policy, governments or legislatures? A long tradition attributes policy outcomes to executives, treating parliaments as passive arenas and reinforcing the parliamentary decline thesis. We challenge this view by advancing a theory of legislative political environments that structure policy outcomes by defining the space of politically feasible policies. We operationalize legislative political environments as seat-share-weighted ideological distributions of all parties in parliament and test whether they are better predictors of policy outcomes than executive preferences in 178 legislatures between 1970 and 2019. Across eleven outcomes spanning welfare universalism, immigration restriction, LGBT inclusion, and climate change, legislative political environments consistently outperform the largest party positions, legislative median positions, and governments' positions. Results hold across regimes, electoral systems, and institutional settings. These findings bring parliaments back to the centre of policymaking research, reframe the partisan theory of public policy, and provide normative implications for electoral participation.