The most widely accepted measure for calculating income inequality is a century-old formula called the Gini coefficient. It’s a gold standard for economists around the globe, along with the World Bank, the CIA, and the Paris-based Organization for Economic Cooperation and Development. What it reveals is startling. Today the United States has the most unequal society of all developed nations. America’s level of inequality is comparable to that of Russia, China, Argentina, and the war-torn Democratic Republic of the Congo.