There is no simple statistic out there for you, like I said, it depends on the group. The RP population overall has dwindled so the times I see open RP is less than before, but that doesn't necessarily mean it all moved to /party. Basically from my experience, some groups are extroverted others are more introverted, with regards to communication channels. I personally don't mind /shouting IC'ly if my character is shouting... others would have OOC problems with that.
I’m the bullies you hate, that you became.