In his book Ages of Discord, the scholar Peter Turchin proposes a structural theory of political instability based on societies throughout history. He suggests that there are 3 main preconditions to revolution: 1. Elite oversupply and disunity; 2. Popular misery based on falling living standards; and 3. A state in fiscal crisis. He uses a host of variables to measure these conditions, including real wages, marital trends, proportion of children in two-parent households, minimum wage, wealth distribution, college tuition, oversupply of lawyers, political polarization, income tax on the wealthy, trust in government, and other factors.