Constituency Diversity and Party Competition: A County and State Level Analysis

One of the staples of American politics is the theory that party competition is a function of constituency diversity. In Federalist #10 (see Rae and Taylor 1970: 7; Fiorina 1974: 89-119; Sullivan 1973) Madison emphasizes that increased constituency diversity facilitates factional dispute. As diversity increases, it weakens the ability of any single faction to represent the multifarious demands of people in a geographic area (The Federalist Papers 1961: 77-83). Despite this relatively simple and normatively pleasing explanatory perspective, and despite this theory's broad acceptance in political science, the study of the relationship between constituency diversity and party competition has been one of the more elusive and sometimes contradictory research topics of the past 30 years. This article analyzes county level data from the 1970s and 1980s-the period that forms the basis of much of this literature-to assess the theoretical and empirical purchase of three of the dominant operational definitions for constituency diversity and then compares these county level findings with parallel state level analyses. I find that reformulated Lieberson/Sullivan social diversity indexes and Koetzle's political diversity index produce similar results at the state and county levels of analysis. Moreover, these results are consistent with the theory that constituency diversity has a strong influence on the level of party competition. One of the staples of American politics is the theory that party competition is a function of constituency diversity. Its prominence in the study of American politics dates back to James Madison's writings on the U.S. federal system of government. In Federalist #10 (see Rae and Taylor 1970: 7; Fiorina 1.974: 89-119; Sullivan 1973; Barrilleaux 1986) Madison emphasizes that increased constituency diversity facilitates factional dispute. As diversity increases, it weakens the ability of any single faction to represent the multifarious demands of people in a geographic area (The Federalist Papers 1961, 77-83). Even though Madison did not foresee the development of political parties in Federalist #10, his logic strongly suggests that party competition develops in response to constituency diversity. Despite this relatively simple and normatively pleasing explanatory perspective, and despite this theory's broad acceptance in political science, the study of the relationship between constituency diversity and party competition has been one of the more elusive and sometimes contradictory research topics of the past 30 years (Sullivan 1973; Bond 1983; Fiorina 1974; Patterson and Caldeira 1984; King 1989; Kenney and Rice 1985; Barrilleaux 1986; Rae and Taylor 1970; Koetzle 1998). Much of this confusion can be traced to the multitude of methods used to measure constituency diversity. Even though some studies measure constituency diversity using common census and demographic statistics, e.g., population, urbanization, income, race, etc. (Barrilleaux 1986(1); Patterson and Caldeira 1984), another group of studies use more methodologically sophisticated measures of social (Sullivan 1973; Bond 1983; Fiorina 1974) and political diversity (Koetzle 1998). Not surprisingly the findings obtained depend on which measure of constituency diversity used. The multiplicity of methodologies and findings underscore the point that this area of research lacks a clear theoretical and operational definition of constituency diversity. In joining this debate, I have two goals. The first is to resolve the confusion regarding the methodology and measurement of constituency diversity in relation to party competition. In pursuing this goal, I analyze county level data from the 1970s and 1980s-the period that forms the basis of much of this literature-to assess the theoretical and empirical purchase of each of the dominant operational definitions for constituency diversity. The second goal is to compare these county level findings with parallel state level analyses to assess the consistency of the relationships and the validity of previous research. …