This topic was rigorously debated last year at my school.
You guys were talking earlier about the age for licenses in Australia before, well in Vic you get your learner's at 16 do 120 hours and when you turn 18 go for your red probationary license. But when you turn 18 you are now legally allowed to drink alcohol.
On two occasions I know of people (one close friend, other only knew of) on their red P's who have had serious accidents and were found to have alcohol in their system.
The problem here is not raise the age at which you can get your license but to raise the age you are allowed to purchase and consume alcohol. By raising that to 21 here at least it makes it harder for P platers to get their hands on it.
Other than alcohol the main contributors to road accidents are inexperience and fatigue.
So by lowering the age at which you get your L's to 14 or 15 to give more experience in the hands of an adult would prove much more effective. That and getting a good night sleep.