Alternative Songs is a record chart published by Billboard magazine 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. On the chart week of 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 which took effect on the chart issue dated January 22, 1994.