When I became a Master Diver I was mentioned in the dive shop's newsletter and they indicated that it's a level less than 2% of divers reach. Now I am a Divemaster so I'm thinking I'm probably now in the top 1% of divers.
I wouldn't be surprised to find more people become PADI Divermasters than get the PADI Master Scuba Diver cert. I know a lot of instructors and DM's... but I don't know anyone that got MSD first. For me it was OW, AOW, nitrox, Rescue, DM, and then the IDC.
So... I would think, just based on my personal experience, that divers who do MSD and then also become DMs are much less than 1% of the diving population.