The numbers would go down by half, which is meaningful, but also way less than you'd want it to. I can't be arsed to pull up the NHTSA data url right now, but I use the factoid all the time when I talk to people about my riding: give or take 54% of motorcycle deaths are single vehicle accidents. Of those, the vast majority involve alcohol or speeding. So if I avoid alcohol I cut my chances by a large factor.

Speeding is slightly fuzzier, because the statistics are built from crash reports by police, and you can never know if they take the word of a witness that a motorcycle passed at a 4mph difference in speed, which, c'mon, is not the same as someone whizzing down a canyon road at 20mph or more over the limit.