I've had the same question in mind, it will help if we could see that stats.
I don't know what type of statistics we should look for in order to know the percentages of signed in / out searchers / googlers.
by the way, my CTR has not been affected, but it got better:
November (first 15 days): 5.50% CTR
December (first 15 days): 7.00% CTR + (PPC improved)
I didn't make any changes to the site.
my view: it all dependence on the sector you are in.