[JAS84]

The charts themselves are flawed nowadays due to streaming. Any song from an album can now chart in the singles chart, and a song could be out of print in physical media but still top the charts thanks to downloads - often happens when someone dies and everyone decides to listen to their back catalogue at the same time. The chart company had to implement rules to stop one act having too many entries in the chart at once, and to weight it so that new releases rank higher than old ones.