The term “global inequality,” measured by the Gini coefficient, refers to the income disparity between all citizens of the world. Global inequality began to dip about two decades ago and continues to do so today, driven by the rise of Asia, particularly China.
From the advent of the Industrial Revolution in the early nineteenth century to about the middle of the twentieth century, global inequality rose as wealth became concentrated in Western industrialized countries. It peaked during the Cold War, when the globe was commonly divided into the “First World,” the “Second World,” and the “Third World,” denoting three levels of economic development.
https://www.foreignaffairs.com/world/great-convergence-equality-branko-milanovic?stream=business