How many Cub scouts earn super achiever award?

The "Super Achiever" or "Heavy Shoulder Award" is an informal distinction bestowed by the Pack on WEBELOS scouts that earn all 20 activity pins. Since it is not an actual BSA badge or award I doubt there are any statistics available.

My personal experience is that it is about 5-10% of bridging WEBELOS (finishing Cub Scouts and moving to Boy Scouts) with about half or less of all Cub Scouts bridging.