The OCC's charts are based on sales data from a panel of around 10,000 music retailers, including all of the major chains and a number of independent stores. The data is collected electronically and fed into a central computer system, which processes the information and produces the charts.
The OCC's charts are calculated using a weighted system, which means that some sales are counted more than others. For example, sales of physical singles and albums are counted more heavily than sales of digital downloads and streams. This is because physical sales are generally considered to be more indicative of an artist's popularity than digital sales.
The OCC's charts are also based on a rolling week, which means that they take into account sales over the past seven days. This helps to ensure that the charts reflect the most up-to-date trends in music sales.
The OCC's charts are published every Friday at 5pm. They are available on a number of platforms, including the OCC website, the Official Charts app, and in the print edition of Music Week magazine.