New statement (see screencap) from staff: Flickr Help Forum Post
Then how this (2016)?
This from a couple of years ago…
Flickr expects us to believe that something other than the algorithm is responsible for 2% of the population getting 50% of the Explore slots? The only other thing that seems probable is that Pro users are much more active than the majority of users, which leads to Explore success.
However, is it even plausible that Pro users, which comprise just 2% of Flickr membership, account for 50% of activity on Flickr?