Andrew Leigh finds that, on average, 63 per cent 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. He finds that male unionists were more pro-Labor than female unionists in the 1960s, but the reverse is true today.