Australia’s Labor and Green parties have reached a support agreement. The Greens won their first House of Representatives seat at the recent election. One seat, out of 150, on over 11% of first-preference votes.

One of the provisions of the agreement is that Green Senator Bob Brown will reintroduce as a Private Members Bill the Commonwealth Electoral (Above-the-Line Voting) Amendment Bill 2008. The Labor party “will consider” the bill. Among other provisions, this bill would allow voters who vote for a party ticket in Senate elections, rather than rank their preferences across all candidates running, to rank the parties in order of preference.

The agreement also includes several proposed reforms to parliamentary procedure, including guaranteeing minor parties the right to ask questions of the Prime Minister no later than the sixth question during Question Time. It further stipulates that the parties acknowledge that any of the Green’s policies for the 2010 election can be brought forward for discussion in parliament. Greens will receive Treasury briefings. There will be a “well resourced Climate Change Committee.”

All in all, a very fine agreement. There is just one catch: the Labor and Green parties remain short of a majority in the House by three seats. There are four independents, whose votes could still give the Coalition (of Liberals and Nationals) a majority if they choose to swing that direction.

The Labor and Green parties appear to have combined for over 49% of the first-preference votes, compared to around 44% for the Coalition. Yet Labor and Greens have just under 49% of the seats, despite the use of a “majoritarian” electoral system (and one that is often taken as a model here in the USA), and despite the fact that the electoral swing from Labor to the Greens was greater than that to the Coalition.

(All claims about the partisan breakdown of first-preference votes need to be taken cautiously until all votes are counted, but the pattern of swing is clear.)