Should the voting age be lowered to 16?

Green MP Sue Bradford has drafted a Private Member's Bill aimed at reducing the voting age from 18 to 16.

DPF over at Kiwiblog has had this to say on the issue:

"Sure one can argue for 16. You can also argue for 12? Or even eight? I mean at eight years old I had a view on who to vote for. All age restrictions are somewhat arbitrary."

This is where his argument is quite weak. There is in fact a rational age at which people should be able to start voting, and that's 16.

Say for instance that we based voting age on ability to comprehend the relevant issues involved with the voting/political process. Quite a reasonable idea I think most people would agree.

Well, IQ research has found that scores in IQ tests flatten out at the age of 16 (or shortly before or after). http://www.psychologicaltesting.com/iqtest.htm

So, apart from probably having read a bit more, the average 18 year old is no more qualified to make an informed decision when it comes to voting. On the other hand the average 16 year old has a substantial advantage over the average 14 year old because their comprehension skills are substantially higher. So by this reasoning it can be said that 16 is the least arbitrary age to allow voting to start.