Pop Airplay
Pop Airplay (formerly known as Pop Songs, Mainstream Top 40 and Top 40/Mainstream) is a 40-song music chart published weekly by Billboard magazine that ranks the most popular songs of pop music being played on a panel of Top 40 radio stations in the United States. The rankings are based on radio airplay detections as measured by Nielsen Broadcast Data Systems (Nielsen BDS), a subsidiary of the United States' leading marketing research company.