A proportional representation election method allocates each party a number of seats in the legislature (or other elected body) proportional to how many votes were cast for that party. Thus, for example, if there are 360 seats up for election, and a quarter of the votes cast are for Libertarian Party candidates, then 90 of the seats will be apportioned to Libertarian Party candidates. There are many different ways of determining which Libertarians get those seats, such as single transferable vote or a party list. There are also many semi-proportional representation systems in existence, including cumulative voting, a relatively simple system that is well-suited to use by corporations, which allow proxy voting, voting trusts, and other binding contractual arrangements, and which allocate votes based on number of shares held.
One argument against proportional representation is that it gives minor parties too much influence, since major parties depend on them, and therefore typically must make concessions to them, in order to form governing coalitions. Under a single member district plurality system, however, the same issue can arise, since a major party will feel compelled to offer significant concessions to a third-party candidate in order to get him to drop out of the race and endorse their candidate. Within the U.S. Libertarian Party, Bill Redpath has been a strong supporter of proportional representation.