Concentrated Post-2020 Sigma Widening: Metric Sensitivity and Persistent Income Hierarchies in Cross-Country GDP per Capita Data

Post-2020 changes in cross-country log GDP per capita dispersion are directionally consistent across macroeconomic data systems but concentrated in a few country trajectories. Using the IMF WEO 1980–2024 baseline, a provisional 2025 extension, and a 167-country WEO–WDI–PWT panel for 2000–2023, the analysis compares sigma, level inequality, weighting, contributions, mobility, and horizon. Sigma rises by 0.018–0.024 across the sources. Paired country-resampling intervals support sign stability, not broad-based widening. The top five contributors account for 60.3–66.9% of the variance increase and the top ten for 86.6–96.3%; positive residuals remain after joint exclusion. The WEO 2020–2024 increase was exceeded by only two of the 36 preceding four-year changes, although sigma in 2024 remained below its 2000 level. Gini and Theil decline or remain approximately flat, while fixed-quartile separation and persistent ranks locate the change within a durable hierarchy. The contribution is an integrated diagnostic of scale, weighting, concentration, persistence, and horizon; it neither measures global interpersonal inequality nor establishes a structural reversal of long-run convergence.