I am using the Trackitt % from last year. I adjusted EB2-I to account for CO's statement that the limit was reached at the end of April, but I was within a few visa numbers anyway.
The EB2-I number is pretty accurate I think. China isn't very well represented, so the error margin is wider for them.
PS I'm off into the wilds with no internet access shortly. I'll be back late Monday and will update everything then, including adding that thread in the FACTS & DATA section (unless I get eaten by a bear or bitten by a poisonous snake).