Lower accident rates, or a lower percentage of injury or fatal accidents? I find it hard to believe 80 year olds are getting into fewer accidents than 40 year olds unless it’s because they drive less frequently.
Which would be fine for an insurer of course. Heck, even if they got into more incidents, but the incidents were cheaper, that would be fine for an insurer too.
And not all markets are equally competitive. Just because insurance rates differ doesn't mean risks necessarily do the same way. And let's not forget that while insurers are professional risk assessors that doesn't mean they're infallible either, or immune to other distortions (e.g. pass-the-buck subprime mortgage kind of issues).
