I added all my numbers to this list a year or two ago and shortly after the spam calls started. Even on numbers that are not publicly used. (I have Google voice as my primary number and it calls my mobile number and a voip desk phone. Now all three get spam calls. I had them for years and the voip and mobile numbers were previously clean. )
I posted this elsewhere in this topic, but my experience with the Federal Do Not Call list was the exact opposite - they promised "within 3 months the calls would stop" and sure enough, within 3 months I never got another call.
Fair, I just checked and it looks like my number was already in the registry when they started getting worse a few years ago. (so adding it again probably did not cause the increase) You can use the site to see if you are already in, and when you were added. one of my numbers was added long before I had it.
