Here is a little project I am working on. It’s a Latin motto generator. I will be adding more patterns soon, hopefully. And it is not difficult to expand the database.
L&S:
ex always before vowels, and elsewh. more freq. than e; e. g. in Cic. Rep. e occurs 19 times, but ex 61 times, before consonants–but no rule can be given for the usage;
I said usually, but I didn’t realize that it was so infrequent with Cicero. At first I thought it might have been letters v. orations, but a quick search through Perseus proved that wrong. Are there any other stats that you are aware of? What about further back?