In areas of tort liability, it's routine for there to be a determination that party A is liable for X%, B is liable for Y%, etc..
Historically, I don't think this would come up as much in copyright law. General torts often involve a confluence of events triggered by multiple actors, whereas copyright violations have usually been clearly the act of a single person or entity, so I'm not sure there's much case law around this.
Historically, I don't think this would come up as much in copyright law. General torts often involve a confluence of events triggered by multiple actors, whereas copyright violations have usually been clearly the act of a single person or entity, so I'm not sure there's much case law around this.