Billboard Hot 100 is a single song.
 On March 24, 2012, Billboard premiered its On-Demand Songs chart, and its data was incorporated into the equation that compiles the Hot 100
Before Nielsen SoundScan, year-end singles charts were calculated by an inverse-point system based solely on a song's performance on the Hot 100 (for example, a song would be given one point for a week spent at position 100, two points for a week spent at position 99 and so forth, up to 100 points for each week spent at number one)

