Baseball: Understanding RBI

From deans-list.net...:

You can't pluralize something that's already plural, and Runs Batted In is no different. RBI is the most versatile of acronyms - it denotes a Run Batted In when a batter knocks in only one run and Runs Batted In when a batter drives in two or more runs. Either way you look at it, singular or plural, RBIs don't exist, but RBI does...

[Edited on 9/4/04 by deanchristopher]