Short answers, pulled from the story.
Economic inequality measures the distribution of income, wealth, or consumption among people. It is quantified using a Gini coefficient where 0 represents perfect equality and 1 represents maximal inequality.
Countries with a Gini index value above 50% include Brazil, Colombia, South Africa, Botswana, and Honduras. These nations face high levels of economic disparity compared to countries like Austria, Germany, Denmark, Norway, Slovenia, Sweden, and Ukraine which fall below 30%.
In 1820, the ratio between the income of the top and bottom 20 percent of the world's population was three to one. By 1991, that ratio had grown to eighty-six to one before recent convergence trends emerged.
Research by Richard G. Wilkinson and Kate Pickett found higher rates of health and social problems in countries and states with higher inequality. Studies link widening income inequality to surges in deaths of despair including suicide drug overdoses and alcohol related deaths.
Economists link automation to increases in economic inequality as it raises returns to wealth while contributing to stagnating wages at the lower end. Stock ownership favors higher income and education levels resulting in disparate investment income for those groups.
The United Nations Sustainable Development Goal 10 aims to garner international efforts in reducing economic inequality considerably by 2030. A 2014 UNDP report warned that greater investments in social security jobs and laws protecting vulnerable populations are necessary to prevent widening income inequality.