Yoda's backwards speech has become a trademark of his. In recent adaptations, it seems like it goes a bit too far. I've always been of the opinion that Yoda's backwards speech was more frequent when he was pretending to be a crazy swamp creature than when he was actually serious. So I took it upon myself to find every line of dialog Yoda has in the Star Wars movies, then classify them as odd or not. Here are the breakdowns I came up with.

ESB, "crazy swamp creature": 13/23 lines are odd, 57%
ESB, serious Yoda: 30/73 lines are odd, 41%
ESB Total: 43/96 lines are odd, 45%
RotJ Total: 18/33 lines are odd, 55%
TPM Total: 19/26 lines are odd, 73%
AotC Total: 31/56 lines are odd, 55%
RotS Total: 46/66 lines are odd, 70%

What I get from these numbers is that Yoda's speech patterns in the prequel trilogy do seem to border on parody at their frequency, and his speech pattern after he reveals himself as a Jedi Master are more normal more often.

For example, when Yoda is serious in the OT, he gives lines like this:

"If you end your training now, if you choose the quick and easy path, as Vader did, you will become an agent of evil."

Compare to a similar line from the PT:

"Twisted by the dark side young Skywalker has become. The boy you trained, gone he is, consumed by Darth Vader."

My theory remains that Yoda's iconic speech pattern was something he used to fool Luke on Dagobah, and only slipped into it after that point by habit. Starting with RotJ, the pattern started overtaking the sense behind it, to the point where the character had to say lines backwards because that is what the average fan expected Yoda to speak like.

It could be argued that perhaps "english" was not Yoda's first language, so he would sometimes slip back into the speech pattern of his original language, but that seems like a stretch since it is shown that he can speak well when he wanted to. I'm thinking while I have all of the lines in a spreadsheet about having a linguist friend of mine analyze them to see if the speech patterns are even consistent, or just randomized per line.

I'm not sure what we can do with this information, its just something that bothered me and thought I would lay to rest.

If anyone wants to see the spreadsheet, I can share it from my Google Docs account (like if Frink needed to know in which movie Yoda says a particular word).