Understanding whether the gap between rich and poor country wellbeing is narrowing is really about whether rich and poor groups can be identified in the overall size distribution of the characteristic of interest, and how those respective subgroup size distributions are changing. Here two simple statistics for analyzing the issue are introduced which are capable of discerning, in many dimensions, changes in the underlying distributions which reflect combinations of increasing (decreasing) subgroup location differences and decreasing (increasing) subgroup spreads, which are the characteristics of polarization (de-polarization). When applied in an examination of the distribution of lifetime GDP per capita over time, the population weighted version exhibits de-polarization and the unweighted version exhibits polarization. As a collection of countries, Africa is diverging from the rest of the world regardless of the weighting scheme.
- Overlap measure
- Trapezoid measure