Might as well make it 25 years old as the accident rate for a 16-20 year old is nearly even with the 21-24 year old rate. Accounting for nearly 70% of all accidents
EDIT: While the accident trend drops noticibly from 16 to 25, it doesn't flatten out until 34 years old, in which it stays pretty flat until 75+ in which the chart I was looking at stops. The
Realistically the worst drivers by any comparison are 16 year olds. But move the age to 18 and the worst drivers will be 18, 21 and I beleive they will be 21. Will the curve just shift or will it actually drop? I think both, but it will primarily shift. While alot of maturing happens between 16 and 21, stats show that currently a 21 year old is only ~40% less likely to be in a wreck than a 16 year old. Start drivers out at 21 and I'd bet that number would be pretty close to even.
EDIT 2: Another interesting point, a 16 year old female is less likely to cause an accident than a 24 year old male. Mabey men just shouldn't get a license until 25