title: Partisan Joiners: Associational Membership and Political Polarization in the United States (1974-2004)*
abstract: Associational life may foster political integration or amplify division, depending on how individuals partition themselves into groups and whether their multiple affiliations embed them into concentric or cross-cutting social circles. Starting from this premise, I relate trends in associational membership to political partisanship, and ask if there is any evidence of increased political polarization in the associative patterns of Americans.
  
  
  
  Using GSS data (1974-2004) on affiliations to 16 types of groups, I plot trends and run multilevel models to examine changes over time in the partisan allegiances of group members and patterns of overlapping memberships.
  
  
  
  The often-lamented decline in group membership affects primarily the category of single-group members and is limited to a few types of groups. The density of the network of overlapping memberships has remained stable over time and there are no real changes in the patterns of shared memberships between group types, nor do Republicans and Democrats differ in their patterns of preferential affiliation. Although political partisanship does not drive patterns of group affiliation, group members, especially those affiliated with multiple groups, are more radical in their partisan identification than nonmembers, and most types of groups have become politically more heterogeneous over time.
  
  
  
  The puzzling finding that group types are not becoming more partisan, while group members are, leads to the hypothesis (to be tested in future research) that civil society polarization is occurring at the level of actual groups, and not group types.
authors.affiliation: Princeton University.
authors.forename: Delia
authors.initials: D
authors.lastname: Baldassarri