A chart hit is a recording, identified by its inclusion in a chart that uses sales or other criteria to rank popular releases, that ranks highly in popularity compared to other songs in the same time frame. Chart-topper and related terms (like number one, No. 1 hit, top of the charts, chart hit, and so forth) are widely used in common conversation and in marketing, and are loosely defined. Because of its value in promoting recording artists and releases, both directly to the consumer, and by encouraging exposure on radio, TV other media, chart positioning has long been a subject of scrutiny and controversy. Chart compilation methodology and data sources vary, ranging from "buzz charts" (based on opinions of various experts and tastemakers), to charts that reflect empirical data such as retail sales. Therefore, a chart-topper may be anything from an "insiders' pick" to a runaway seller. Most charts that are used to determine extant mainstream popularity rely on measurable data.
Record chart performance is inherently relative, as they rank songs, albums and records in comparison to each other at the same time, as opposed to music recording sales certification methods, which are measured in absolute numbers. Comparing the chart positions of songs at different times thus does not provide an accurate comparison of a song's overall impact. The nature of most charts, particularly weekly charts, also favors songs that sell very well for a brief period of time; thus, a song that is only briefly popular may chart higher than a song that sells more copies in the long range, but more slowly. As a result, a band's biggest hit single may not be its best-selling single.
According to Joel Whitburn, the American trade publication Billboard introduced the Hot 100 on August 4, 1958. This was the first chart in the US to "fully integrate the hottest-selling and most-played pop singles." From 1958 until 1991, Billboard compiled the chart from playlists reported by radio stations, and surveys of retail sales outlets. Before 1958, several charts were published, including "Best Sellers in Stores", "Most Played by Jockeys" (later revived under the name Hot 100 Airplay), and "Most Played in Juke Boxes", and, in later collations of chart hits, the record's highest placing in any of those charts was usually reported. On November 30, 1991, Billboard introduced a new method of determining the Hot 100, "by a combination of actual radio airplay monitored electronically by Nielsen Broadcast Data Systems (BDS), additional playlists from small-market stations, and actual point-of-sale information provided by Nielsen SoundScan." Until 1998, any songs placed on the chart had to be physically available as a single. The Hot 100 continues to be published.