At least since the sans culottes-literally, "those without breeches"-streamed through the streets of Paris in 1789 to overthrow the ostentatious and corrupt ancien ŕegime, modern social theorists have grappled with the relationship between paoverty and political participation. Connections between people's economic resources and their political activities date back to antiquity, but the appearance in the late eighteenth century of democratic nations with novel forms of mass participation and the onslaught in the nineteenth century of the industrial revolution, with its starkly unequal social classes, led to new speculations about how income inequality produces political activity. Alexis de Tocqueville worried that democratic participation would allow the lower classes to use their political power to level society, erasing all differences (including income inequality) and creating uninspired homogeneity. Karl Marx predicted that capitalism's extreme income inequality would generate working-class consciousness and the revolution of the proletariat, ending in communism. In both formulations, economic inequality would spawn political participation that would transform society. The rapid increase in income inequality in the United States from 1979 to 1994 raises anew the classic concerns of social theorists. Modern social scientists have explored the relationship between income inequality and revolutionary activity across many countries (see, for example, Hibbs 1973; Gurr 1970), and they have investigated the relationship between income and conventional political activities such as voting, campaign work, and campaign contributions by individuals (Verba and Nie 1972; Wolfinger and Rosenstone 1980). Neither of these strains of research, however, adequately addresses the questions raised by the changes in the past thirty years in America. In a stable democratic society such as the United States, income inequality seems less likely to foster revolutionary activity than to erode the conventional activities of some groups and to stimulate the conventional activities of others, leading to changes in who gets what, when, and how. The finding from cross-sectional surveys that political activity increases with higher income captures just part of the story. It says nothing about how over-time increases in income inequality affect political participation. This chapter offers an analytical perspective on income, income inequality, and participation, and it presents new empirical work that goes beyond existing research. The analytical perspective draws on political science and economics to consider how income and income inequality affect participation. The most important contribution of the chapter is the 668 Social Inequality demonstration that changes in income and changes in economic inequality have very different implications for political participation. Income is an individual characteristic stemming from personal capabilities, opportunities, decisions, and luck. Income affects individual behaviors such as political participation because it provides a resource for participation. Nowhere is this more obvious than in political giving. It is not surprising that those with more income make greater contributions to politics and that those with less income make smaller contributions (Verba, Schlozman, and Brady 1995). It also seems reasonable to suppose that when a family moves from a higher income level to a lower one, its contributions to politics will be reduced. But does this necessarily mean that political activity by the lower classes will decrease and that the upper classes' political activity will increase when inequality widens? It does not. Income inequality is a property of society, a social fact about the distribution of incomes. An increase in inequality will not only reduce the incomes of lower-class families but also change that group's political circumstances. With this distressing change in social facts, lower-income people might decide to increase their political activity to redress the situation. They might decide that government should be used to adjust the degree of inequality by adjusting people's capacities, opportunities, luck, or decisionmaking. It seems possible that lower-class activity might increase in these circumstances. It also seems possible that upper-class participation might increase in response. This chapter investigates mechanisms that can explain how income and income inequality affect political activity. There are two goals here. One is to show how changes in income and income inequality can affect political activity in different, and sometimes opposite, ways. The arguments just cited suggest that they should operate differently, but the wellknown positive cross-sectional correlation of contributions and income only suggests that participation should increase with income. The second goal is to specify the empirical tests that might distinguish the impacts of income and income inequality. Thus, the aim is to determine the proper specification of a political activity equation such as: Political Activity a b (Income) c (Inequality) d (Controls) omitted variables, where a, b, c, and d are parameters. This chapter provides insights about how to measure income and inequality, the expected signs of b and c, whether to add an interaction term of income and inequality, and the identity of other variables that affect political activity. The empirical research reported here reveals the seemingly paradoxical result that from the 1970s through the 1990s, participatory inequality decreased for at least some forms of political participation and in some places as income inequality increased. The analytical perspective suggests various reasons why this might be so, and it provides avenues for future research. Although we append an extensive bibliography of articles that we have consulted, this chapter does not provide an article-by-article review of this literature, partly because there are several other excellent literature reviews (Leighley 1995; Schlozman 2002; Verba, Schlozman, and Brady this volume; Freeman this volume), but primarily because the greatest need is for an analytical perspective on this literature that considers the objectives of the Russell Sage Foundation's project on the "social dimensions of inequality." Without such a perspective, the empirical findings are obtuse, recondite, and confusing.