x2, I calculate this way too so I can see if the roosters are on the job, if handling hurt them, etc. I want to know the WHOLE picture. And clears don't necessarily mean not fertile in my book; I need to see a lack of bulls eye on some samples to verify that.
especially with shipped eggs.. since the postal service can trash them pretty easily...
but for my own home grown eggs.. if I have a clear (no blood ring .. no growth) I can be 99% sure it's fertility ... then all I have to do is pull a half dozen eggs from that pen for my husband and myself for breakfast and check bulls eyes!
I pulled the shipped goose eggs that were from Texas (all 6 were clear) and checked for fertility.. 0 bulls eyes... so yeah.. that's pretty much the definitive test for fertility in unhatched eggs if you get them pulled and checked before the protein of the yolk starts to degrade too much