The Bump Scale was developed so pilots could objectively communicate what turbulence they’re feeling or felt. When used properly, an experienced pilot’s 5 will be a new pilot’s 5. That is why it is tied to specific tip collapses. Acro Ace’s 5 is the same a Newbie. If someone says “your 3 is my 1” they don’t get the concept.

There are variations in wings, of course, and techniques to fly them. A highly skilled pilot will better keep the wing overhead and tracking straighter which reduces collapses. A pilot flying a higher performance wing or lightly loaded will be more likely to get small collapses than on a lower performance wing or heavily loaded.

These levels are used in the PPG Bible for standardization. 

Important reference points are: 0 is obviously dead calm, 5 is small tip collapses on a beginner wing with no input and 7 is a 50% collapse on that same wing.