The Digital Songs chart (previously named Hot Digital Songs) ranks the best-selling digital songs in the United States, as compiled by Nielsen SoundScan and published by Billboard. It debuted in the issue dated January 22, 2005, and merged all versions of a song sold from digital music distributors. Its data was incorporated in the Hot 100 three weeks later. Since October 2004, digital sales have been incorporated into many of Billboards music singles charts. The decision was based on the dramatic increase of the digital market while commercial single sales in a physical format were becoming negligible.