Here is a link with some stats, for BWM '03 - '06 and, X5 models specifically...
I knew I had it somewhere; just took some digging in my BookMarks and hunting via the handy Search Tab here.
Unfortunately, BMW stopped breaking out "model stats", within X5s, in '07, at least for semi-public consumption.
And, all this data used to be put up by a good poster named Fred Meloan, whom hasn't posted in a couple of years...
link:
Xoutpost.com - View Single Post - December 2006 X Series Sales Report
Hit the pdf file in the link above. Hope this is of some answer to your question(s).
GL,mD