The document discusses income inequality, which is the gap between rich and poor in terms of wealth and income distribution. It provides data on income inequality ratios between the richest and poorest 10% of populations in various countries. Income inequality varies between societies, economic systems, and over time. There are various ways to measure economic inequality numerically, including Lorenz curves and Gini coefficients. The document then discusses some of the key causes of income inequality like changes in labor markets, globalization, technology, and tax policies. It also discusses some of the impacts and trade-offs of income inequality.