I probably titled my post wrong, because as I look back at it, it isn't really CS% I was thinking about. The question I was trying to address was:
When I am watching my son play games and we discuss the game afterwards, how do we evaluate how well he caught?
We certainly discuss SBA's and CS's. But we both know what Fungo says is true - so many times a SB isn't really a catcher issue.
So I was trying to ask how do other folks evaluate how well a catcher catches and throws?
I've started to pay attention to bases given up without the ball being put in play by the batter. (I don't track them as in keeping a spreadsheet or anything, I just count them each game and talk with Jeff afterward.)
There are three basic ways for a runner to advance on a pitcher-catcher exchange: PB, SB and WP. (Ignore balks).
Clearly, the catcher isn't at fault for WP's, but one catcher might not be able to get to some pitches that end up being scored as WP's, and another catcher might. So as a coach, I'd like to know which kid gets to the ball better.
So it seems to me that bases allowed is a pretty good proxy for how well the catcher catches. Especially over a number of games where the truly unreachable WP's will average out one catcher to the next.
Admittedly, this is far less of an issue the higher the level of play. In HS ball from what I have seen, at the varsity level, I would say there's an average of 4-5 bases allowed each game on the combo of SB, WP and PB.
In college and pro, there aren't as many curves and fastballs in the dirt, so the CS% is probably a better measure there than at lower levels.