First lets examine the systems employed by the US, UK and Australia. Like most governments, the systems in these countries are considered to be divided into three branches, the legislative, the executive and the judicial. The judicial branch is appointed in such a way as to be (in theory at least)politically neutral, while the other two branches are elected.
One of the main features of the US system is a complete separation of the legislative and executive branches of government. The result of this is that the President, who in the case of George W. Bush was elected with a popular vote of only 47.87%, is in complete control of the Executive, accountable to no one.
The most common complaint about the US presidential electoral system is the concept of the Electoral College. It was due to the Electoral College that Bush was able to win the election despite gaining fewer votes in total than the runner-up Al Gore. However another major flaw in the US system is the first-past-the-post system, which guarantees that a vote for a candidate not endorsed by one of the two major parties will be a wasted vote. The minute number of people voting for a minor party candidate in the 2000 presidential election testifies to this fact.
The system employed in the UK improves on this system in one important respect. Instead of the executive branch being voted for separately, the executive is formed by the majority party in the lower house of parliament, and is accountable to it. At least that's the theory. In practice however, the party that controls the Executive generally has a complete majority in the lower house and as such the lower house acts as little more than a rubber-stamp for the decisions of the executive branch. Again this is due to the winner-takes-all nature of the first-past-the-post system. The UK also has an unelected upper house, made up of appointees and hereditary peers, however their powers are minimal.
Australia has managed to make some improvements to the above systems. Like the UK, Australia's Executive government is formed out of the majority party in Parliament. However there are two important differences.
The first is that the lower house in Australia's parliament is voted by a preferential system (also known as instant runnoff). This means that instead of merely ticking the candidate you support on you ballot, you number each candidate to indicate your first, then second, then third preference and so on. The result is that you can vote for a minor party without your vote being wasted - your vote will flow through to your preferred major party if the minor party candidate does not succeed. However in practice the majority of lower house seats go to major party candidates in far greater proportions to the votes they actually receive.
The second difference, which helps to offset the two party system in the lower house, is that Australia's upper house employs a system known as proportional representation. Proportional representation is based on the idea that if your party gets 5% of the vote, then it should get 5% of the seats. While the Australian implementation (which has an equal number of senators per state) does not completely achieve this result, it comes close.
There is one major disadvantage to this system however. That is, it is possible that the lower house and upper house will be controlled by two different parties. This was a problem for Gough Whitlam's government in 1975, where the Senate refused to pass a Supply Bill to fund the activities of the Executive branch. This eventually resulted in the dismissal of the Whitlam government.
Noting the above disadvantage, one might argue that it would be a good idea to have a system with a single house based on a proportional representation system. However there is one disadvantage to such a system. Despite its flaws, the House of Representatives does serve a useful function: it gives each local area access to their own member of parliament who is responsible for representing the people of their electorate. Under a system of proportional representation, each member of parliament would be a part representative of (in the case of the current system) their state, meaning that local issues would rarely get looked at.
The system employed in New Zealand provides a solution for that. Like Australia and the UK, the New Zealand Executive is formed out of members of parliament. However unlike the UK and Australian system there is a single house, elected via a method known as the Mixed Member Proportional electoral system.
Under the New Zealand system, each person casts two votes. One vote decides their local member, the other decides which party they would like to represent them federally. There is a 120 seat parliament, with 62 seats coming from local electorates, 7 from Maori electorates, and the balance appointed based on the proportion voted in the party ballot. This gives the advantages of both the local representative system and the proportional representation system, without the risk of the deadlocks that can occur in a two house parliament.
There are some ways that the New Zealand system could be improved, most notably the first-past-the-post system used for the electorate votes poses the same problems as elsewhere. However overall it would appear to work well, as can be seen from the 2002 election results.
As these results show, seats are awarded in roughly the same proportion as votes received. This means that the party with the most votes still has to negotiate with other parties in order to have policies implemented. And more importantly, it means that minority parties, even if they have no real power, are still able to voice their opinion in parliament.
The concept of "one man, one vote" is fundamental to the system of representative democracy. Likewise it should be fundamental that parties should be given power in proportion to the number of people who vote for them. 40% of people should not have 100% of the power. New Zealand's Mixed Member Proportional electoral system achieves this goal and it is a system well worth looking at by those proposing electoral reforms in other countries.