How Do Unionists Vote? Estimating the Causal Impact of Union Membership on Voting Behaviour from 1966 to 2004

I explore the voting patterns of trade union members in Australian elections conducted between 1966 and 2004, and find that on average, 63 percent of trade union members vote for the Australian Labor Party. Despite the fact that union membership declined from around one-half of the workforce in the early-1980s to one-quarter of the workforce in the early-2000s, unionists have not become more pro-Labor. Analysing unionists’ voting behaviour by gender, I find that male unionists were more pro-Labor than female unionists in the 1960s, but the reverse is true today. Recognising that union membership may be endogenous with respect to political ideology, I instrument for union membership and conclude that the observed association between union membership and voting reflects a causal relationship.