How do unionists vote? Estimating the causal impact of union membership on voting behaviour from 1966 to 2004

This paper explores the voting patterns of trade union members in Australian elections conducted between 1966 and 2004 and finds that, on average, 63% of trade union members vote for the Australian Labor Party. Despite the fact that union membership declined from around half of the workforce in the early 1980s to a quarter of the workforce in the early 2000s, unionists have not become more pro-Labor. Analysing unionists' voting behaviour by gender, it is found that male unionists were more pro-Labor than female unionists in the 1960s, but that the reverse is true today. Recognising that union membership may be endogenous with respect to political ideology, this study instruments for union membership and concludes that the observed association between union membership and voting reflects a causal relationship.