The UK Albums Chart is a weekly record chart based on album sales from Sunday to Saturday in the United Kingdom; during the 2000s, a total of 274 different albums by 170 artists reached number one. The chart was compiled weekly by the Official Charts Company (OCC) on behalf of the British music industry—it listed only physical album sales until 2007, after which it also included albums sold digitally. The OCC defined an "album" to be any music release that featured more than four tracks or lasted longer than 25 minutes. Each week's new number one was first announced on Sunday evenings by BBC Radio 1 on their weekly chart show.