<p>Political diversity, voter engagement, and institutional stability are foundational to effective economic governance and democratic legitimacy. While the literature has extensively examined the impact of voting rules in single-winner elections, the constitutional implications of seat allocation methods in multi-winner parliamentary systems—specifically their impact on party fragmentation—remain underexplored. This article investigates the institutional nexus between seat allocation rules and parliamentary structure in Senegal and Burkina Faso, two emerging democracies with distinct electoral trajectories. Drawing on computational simulations and a comparative analysis using the Laakso-Taagepera Effective Number of Parties (ENP) index, we evaluate six electoral systems—including the D’Hondt method, First-Past-The-Post, and mixed approaches—and their effects on representation, participation, and institutional resilience. Anchored in the framework of constitutional political economy, our analysis considers how electoral rules shape the strategic behavior of political actors. The findings suggest that proportional systems enhance minority representation, though they increase fragmentation (higher ENP), while majoritarian systems promote stability at the potential cost of diversity. These results underscore that seat allocation rules are not merely technical choices but strategic constitutional instruments that mediate the trade-off between representativeness and governance efficiency, with long-term implications for institutional performance and democratic consolidation.</p>