I have to look this up, but I may not have a complete backup of my photo archive — at least not one which is easily accessible. To make matters worse, I have very recently reorganized my photo archive, and in that process, I have peeked into most projects in order to see what they contain — and in that process, I may have erased most of my ratings — inadvertently, of course.
This is all (or most) with raw files (*.NEF), and I have added the ratings in PL, initially with earlier versions, such as PL 4, now with PL 5.x. Adding the ratings is part of my screening and evaluating projects with 500 - 1000 shots each, right in PL, either in the image browser, by clicking on stars, or with the appropriate keys via keyboard. I may be slightly lucky with more recent ones, as there, I have added “picked” and “rejected” tags, so there, I don’t quite need to restart from scratch. I have never worked with XMP files, never even considered in-camera rating…