I'm on vacation, so I won't dig into this right now - maybe someone else will, else I can revisit it when I get back.
But here's a little bit of info: in the 60 days prior to registration being enacted, Programmers got 877 bad* questions from registered users, and 182 from unregistered users, making up 48.05% of those asked by registered and 76.15% of those asked by unregistered users respectively.
In the past 60 days, Programmers got 1314 bad questions from registered users, making up 54.32% of the total asked.
Interpret that as you will...
*closed, deleted, or down-voted below 0.