Many people are aware of Paul Diederich's Word Frequency count and the
Whitaker's Words dictionary web applet that has been built upon it. Diederich also did an Ending Frequency, which includes a list of
Eighteen Common Endings as well as a set of
Rules Governing Variable Endings, plus
The Twenty Two Rare Endings and some
Penultimate Signs. If you are having trouble getting all those inflections straight in your head, you might want to take a look at
The Frquency of Latin Words and Their Endings.