This is a follow up to Does marking an email as spam in Gmail affect the filter for everyone?
In the Gmail web interface, if I go to the spam folder and clear it, this can be interpreted as a confirmation from my side Yes, these are indeed all spams.
Does Google use that action to improve their spam filters?
Best Answer
Only a Google engineer can answer for certain, but...
Based on what I've seen over the years, it's the manual marking as spam or "not spam" that provide the signals to the spam algorithm. This Gmail blog post, for instance, thanks users for using the "Report Spam" and "Not Spam" buttons; no mention is made of clearing the spam bucket. Nor does it get mentioned on this Gmail Support page about spam. This Gmail Support page about reporting spam only talks about the "Report Spam" button. Again, no mention of emptying the spam bucket.
It seems to me that clearing the spam bucket merely indicates that the user wants to get rid of all the junk in there. Maybe to start fresh and start checking spam more closely, maybe because they just don't like that junk hanging around. It doesn't appear to be a signal that Google uses.