This study investigates why Congress fragments implementation power by policy area. We argue that divided party government motivates fragmentation as a strategy to enhance legislative control over bureaucracy.

Data & Methods

We developed a novel measure of policy implementation fragmentation (1947–2008) and analyzed its relationship with separation-of-powers structures using quantitative analysis.

Key Findings

• Divided party government strongly correlates with fragmented implementation power

• This association drives the long-term increase in fragmentation since WWII

• Legislative coalitions fragment implementation more under conditions of high uncertainty about remaining majority status

The results demonstrate how legislative strategies adapt to institutional constraints and political dynamics.