I am looking for some proof, or at least evidence to whether or not sites are being hurt by duplicate content.
The situation is, that there were 4 content rich newspaper/magazine style sites that were basically just reskins of each other. [ a tactic used under a previous regime ] The least busy of the sites has since been discontinued & 301d to one of the others, but the traffic was so low on the discontinued site as to be lost in noise, so it is unclear if that was any benefit.
Now for the last ~2 years all the sites have had unique content going up, but there are still the archives of articles that are on all 3 remaining sites, now I would like to know whether to redirect, remove or rewrite the content, but it is a big decision - the number of duplicate articles? 263,114 !
Is there a chance this is hurting one or more of the sites? Is there anyway to prove it, short of actually doing the work?