The nice thing about this one is that I think everyone is as likely as anyone else to get one. OK so the more projects / SubProjects you have worked on increases the odds a fair bit, but someone could have worked on 5 projects and have one or two of these and quite probably wont know why! I always got the impression that you were quite keen on mysterious ones Bok.
I do think the 0.1% tolerance would make a difference if you haven't already got it in there. I would have thought that they will be far more commonplace with that tweak. Or would it be easier to just arbitrarily say plus or minus 500 say, or some such? I'm not bothered, but I suspect you will find more of them with percentages. Why not have a look at the data and pick what you think works best.