The UK Albums Chart is a music chart compiled by the Official Charts Company (OCC) that calculates the best-selling albums of the week in the United Kingdom. Initially based solely on the sales of albums in the vinyl and CD formats, digital albums began being included from April 2006. Since March 2015, the chart has also been based on audio streaming figures, however the OCC still compiles a 'sales' (only) chart and still quotes these traditional sales figures in its features and articles. Note: The 21st century actually began in 2001.