A record chart is a ranking of recorded music according to popularity during a given period of time. Examples of music charts are the Hit parade, the Billboard Hot 100 or Top 40.
Many different criteria are used in different charts, including sales of records, cassettes and compact discs, the amount of radio airplay, and since the introduction of digital technology, the number of downloads and the amount of streaming activity.
Some charts are specific to a particular musical genre and most to a particular geographical location (although download charts are not easily pinned down in this way). The most common period of time covered by a chart is one week with the chart being printed or broadcast at the end of this time. Summary charts for years and decades are then calculated from their component weekly charts. Component charts have become an increasingly important way to measure the commercial success of individual songs.