Voting is an important activity in a democracy. Elections decide the fate of a country for a specific period apart from its long term impact. In most countries the voting age is around 18 years.The youth are a volatile group who are swayed by personal considerations rather than public good. In my opinion these young people are not mature enough to choose the right candidate. Being children themselves how can they choose a suitable adult who is going to govern. Youth are fascinated by money, cinema and other entertainment. They may not understand what public good is. amirite?
Age is the only variable which can be universally applied. All other specifications such as "married people" etc. etc. may become highly subjective. When people reach certain age say 21 years or more it is likely that they might have been exposed to the complexities of life and therefore will be in a position to understand what is personal and how it affects the interest of the public. Understanding the functioning of societies is the most important aspect that will decide the quality of voting.