This repository contains the documentation and validation framework for the Power-Sharing Index (PSI). The PSI is a longitudinal measure designed to track cross-group power-sharing and inclusive governance from 1789 to the present.
The PSI defines power-sharing as the substantive inclusion of diverse groups in the political process. Five items were selected from the V-Dem (Varieties of Democracy) dataset based on three criteria:
- Temporal Depth: Continuous data from 1789 to the present.
- Historical Sensitivity: Ability to accurately score the low inclusivity of the Herrenvolk era.
- Distinct Mechanisms: Capturing unique facets of exclusion.
| Variable | Mechanism Captured |
|---|---|
| Group Power | Distribution of political power among social groups. |
| Gender | Women's political empowerment and inclusion. |
| Civil Liberties Equality | Equal protection of rights across different groups. |
| Physical Integrity (Torture) | Freedom from state-sponsored torture. |
| Physical Integrity (Killings) | Freedom from political killings. |
Note: Variables such as Suffrage were excluded because they lacked historical coverage back to 1789 or failed to capture non-electoral nuances of exclusion.
Statistical testing confirms that the PSI components measure a single, cohesive underlying construct.
- Inter-item Correlation: All items show high synergy (> 0.60).
- Cronbach’s Alpha: ≈ 0.96, indicating exceptional internal reliability.
- Principal Component Analysis (PCA): PC1 explains 87.4% of the variance, with high loadings across all components.
- KMO Measure: ≈ 0.79, confirming "good" sampling adequacy for factor analysis.
The PSI’s performance was benchmarked against historical eras to confirm discriminant, convergent, and construct validity.
- The Herrenvolk Paradox (1789–1899): The PSI shows a negative correlation with Electoral Democracy, identifying that early democratic expansions often coexisted with deep group exclusion.
- Modern Convergence: Strong positive correlations with V-Dem indices post-1965.
- Event Sensitivity: The index reflects documented shifts around the 19th Amendment, the Voting Rights Act of 1965 (VRA), and the Shelby County v. Holder (2013) decision.
To ensure the index is not dependent on a specific mathematical formula, we tested multiple aggregation methods:
- Comparison: Additive, Multiplicative, and Hybrid methods were compared; all yielded consistent temporal patterns.