I was playing around with a new stat in my head the other day, so I thought I'd flesh it out here. I know I've been beating the "RBIs are useless" drum on the Flushing University message board, so I figured I'd try to find a way to contextualize it.
It's not that RBIs themselves are useless - it's that comparing two players with a counting stat that's dependent on so many other variables is not a good measure of offensive ability. I'm calling it "RBI Opportunity Percentage" - or RBI% for short.
Here's my theory - when runners are on base, the ultimate goal of any subsequent at-bat (except in the event of a sacrifice bunt without a man on third base) is to drive those runners in. It's not fair to look solely at RBIs as a measure of effectiveness, because a player with 300 chances to drive in runs is going to have more RBIs than a player with 200 chances.
So here's what I did: I looked at a player's number of plate appearances with runners on base and their RBI totals in those situations. I subtracted the number of home runs from those RBI totals, because it unfairly benefits the home run hitter to leave them in. (Yes, I know that makes this a somewhat flawed stat right off the bat, so feedback is encouraged.)
Then it's simple: take the rest of the RBIs and divide them by plate appearances. Let the result go three decimal places (so it looks like batting average, on base percentage and sluggng percentage) and you have RBI Opportunity Percentage. I think it's a better measure of ability than RBIs, because it puts everyone on a theoretically equal playing field and rewards the hitter who makes the most of his opportunities.