It's actually the lack of air pollution that makes the difference.
LA has a SPF 30 sitting above it for most of the year. For most of the time, Australia does not.
Interesting. Do you have a source for that? I have wondered what the actual reason is for a while.
closer to ozone hole, more uv
Its also one of the reasons tourists get such bad sunburns here as they hit the beach without any protection.