Alternative Airplay is a record chart published by the music industry magazine Billboard that ranks the most-played songs on American modern rock radio stations. Introduced by Billboard in September 1988 and named Modern Rock Tracks until June 2009, it was initially compiled based on weighted reports from several national rock radio stations. Starting with the chart dated June 12, 1993, radio airplay data compiled by Nielsen Broadcast Data Systems – which electronically monitors various radio stations on a daily basis – was introduced as a factor in determining chart rankings. Modern Rock Tracks later became solely based on Nielsen data, a change that took effect with the chart dated January 22, 1994.