Hey AAF. This is a perfect example why so many vets suggested you wait longer before modding a game. You need to know the answers to questions like that (plus more complicated ones) without having to ask.
Now, the exact proportion varies from one game to another, one format to another, even from one game mod to another because other factors come into play. But it's still the basic mafia game dynamic where a minority of informed players (scum) goes against a majority of uninformed players (town).
As a general rule of thumb, estimate that percentage is going to be approx. 25% evils vs 75% innocents. Just remember this changes a lot.
I've seen games where less than 25% were scum, something like 19% or so. And I remember it's been as high where 33% of the players were scum.
