So if one person rents a DVD every week and now pirates, there would have to be someone who rented 50 MORE DVDs (or purchased) than they would have had there be

So if one person rents a DVD every week and now pirates, there would have to be someone who rented 50 MORE DVDs (or purchased) than they would have had there been no pirating options. On what concrete evidence do you base this? Please don't tell me that every unauthorized copy would have been a sale or rental had unauthorized copying not been an option because I'm fairly certain you have no way of possibly knowing that. (If you do have a way of knowing that then I'm all ears as to your methods.)