You said: 60% of accidents are caused by SOBER drivers.
That means 40% are caused by drunk drivers. What percentage of drivers are drunk on the road at any one time? I'd bet MUCH less than 40%....
After about 2:00 am , (I have heard) the overwhelming majority of drivers are intoxicated.
Take the total population of drivers, divide them into subsets of drunks and non drunks and compare the accident rates.
I bet drunks have fewer accidents percentagewise than sober drivers.