A flaw of the 1-man-1-vote system in a proportionally-representative electoral system involving more than 2 contestants

In a democratic political system with more than 2 political parties, a proportionally-representative voting system will not necessarily lead to the most socially optimal outcome. Let me use an example to illustrate this. For example, Thailand has 3 political parties – the rural populist People's Power Party(PPP), the royalist Democrat Party (DP) and the neutral party For The Motherland (FTM). Next, we have two major supporter groups with different preferences of political parties to form the government- The National United Front of Democracy Against Dictatorship(UDD) which is pro-PPP and anti-DP, and the People's Alliance for Democracy(PAD) which is Pro-DP and Anti-PPP. The neutral FTM party is ranked second in preference to both political support groups. Here is a table showing the ranking of the preferences of the 2 groups of supporters.






The objective of an electoral system is to obtain a government that is most socially optimal, that is that the majority of the voters can be reasonably happy with the elected government. If we interpret “reasonably happy” as the voter being able to get his first or second choice, then the most socially optimal political group would be the FTM as it is ranked second in preference for both support groups. Both support groups would be contented with a FTM government than to have a government of the political party they oppose.

However, in an electoral system with only one vote per person,an individual does not have the ability to reflect his preference of the second-best government. Only the top preference of an individual is reflected in the votes. When the votes are tallied up, the results is that the FTM garners the least votes as people from the UDD and the PAD spend their votes on their respective topmost preferred political party. The FTM would hence lose out in the political race.

Such a flaw in the voting system can also be applied to public-polled popularity competitions such as Singapore idol. A contestant who is generally well-liked by the general public may still have a higher chance of being eliminated than a contestant with a smaller but more fervent fan base.