Billboard magazine compiled the top-performing dance singles in the United States on the National Disco Action Top 30 chart. Premiered on the issue dated August 28, the chart ranked the popularity of singles in nightclubs across the country, based on a national survey of club disc jockeys. Previously, Billboard started the Disco Action survey in 1974 which ranked the popularity of singles in New York City discothèques, expanded to feature multiple charts each week which highlighted playlists in various cities such as San Francisco, Boston, Los Angeles, Chicago, Miami, Phoenix, Detroit and Houston. The next year, Billboardâ²s rival publication Record World was the first to compile a dance chart which incorporated club play on a national level. Billboard statistician Joel Whitburn later "adopted" Record Worldâ²s chart data from the weeks between March 29, 1975, and August 21, 1976, into Billboardâ²s club play history. For the sake of continuity, Record Worldâ²s national chart is incorporated into the 1975 and 1976 lists.