 Nielsen BDS was introduced in "Billboard" in January 1990 and first used on the "Billboard" Country music chart.It was adopted for the Hot 100 Airplay on the issue dated December 8, 1990, and on the Hot 100 with the issued dated November 30, 1991.BDS measures actual airplay by monitoring radios stations continuously with computers that "listen for the unique 'audio fingerprint' of each song and register a detection every time a song is played."