Where did I get my data? The SWAG method, compounded with wild conjecture and personal observation. I've met quite a few folks who would legitimately be required to have a 107 for uses that are really no different than standard hobbyist flying, simply because their hobby temporarily intruded on a for-profit venture they were involved in. On the other hand, as far as "pro" drone operators whom I've met, let me add them up a bit.... um, uh, carry the two, um........ Zero. A similar number of the first group had a 107, despite the requirement to do so. I did see one bunch on the side of the road with a big two-operator rig a few months ago doing power-line surveys, just flying a bunch of rural distribution lines to mark where the brush needed cut back out of the right of way. Didn't talk to them, but they're the sum total of my personal exposure to somebody who would NEED the current iteration of the 107 certification or higher..
I haven't seen anybody here discount what would happen if a drone and a manned aircraft attempted to share the same airspace at the same time. That being said, you could just as easily just say that a 15 year old kid in Wyoming shouldn't be able to fly a Mavic in his backyard when Elon Musk is launching something in Florida, just because the risk is too high. At some point you just have to step back and realize that the risk just doesn't justify the efforts to mitigate it. If a farmer flying a one-pound drone 200 yards from his house at 50' altitude is a risk to General Aviation, then there's something wrong with the General Aviation in the area. The flying I'm talking about here is of no greater risk than any of the "hobbyist" flying, probably much less just by virtue of the fact that it's around a ground-based foci, plus the fact that it's probably somebody using the drone as an expensive tool that you just can't afford to take risky chances with, rather than just some kid seeing how high he can take the thing. It's certainly nothing that the basic existing safety rules and laws don't cover, with or without the 107.
If you want to call it sour grapes, fine. I just don't see any possible way that the current 107 test material has even the slightest applicability to the folks I'm talking about here: none. Zilch. No improvement in public safety, no reduced threat to manned aviation, no improvement of homeland security. None whatsoever. As this thread started as, it's ridiculous overkill for the need/risk/threat in the flying I'm talking about.