The Billboard 200 is a listing of the 200 highest selling music albums in the United States, published weekly in Billboard magazine. It is frequently used to convey the popularity of an artist or groups of artists. Often, a musical group will be remembered by its "number ones", those of their albums that outsold all others during at least one week.
Billboard began publishing album charts on March 24, 1945, expanded to the current size and name on March 14, 1992. Since May 26, 1991, the Billboard 200 positions have been derived from Nielsen SoundScan sales data, currently contributed by approximately 14,000 music sellers. Because these numbers are supplied by a subset of sellers rather than record labels, it is common for these numbers to be substantially lower than those reported by the Recording Industry Association of America when Gold album awards are announced (RIAA awards reflect wholesale shipments, not retail sales).
The Billboard 200 can be helpful to radio stations as an indication of the types of music listeners are interested in hearing. Retailers can also find it useful as a way to determine which recordings should be given the most prominent display in a store. Other outlets, such as airline music services, also employ the BIllboard charts to determine their programming.
The chart omits unit sales for listed albums and total recorded sales, making it impossible to determine, for example, if the number one album this week sold as well as the number one from the same period in the prior year. It is also impossible to determine the relative success of albums on a single chart; there is no indication of whether the number one album sold thousands more copies than number 50, or only dozens more. All music genres are combined, but there are separate Billboard charts for individual market segments. The complete sales data broken down by location is made available, but only in the form of separate SoundScan subscriptions.
According to the December 1, 2001 issue of Billboard, Pink Floyd's Dark Side of the Moon has been on the charts for a total of 1,285 weeks, or just under 25 years. Its closest rival is James Taylor's Greatest Hits, checking in at 573 weeks on the chart. Taylor can expect to reach Pink Floyd's record number in about 13 1/2 years.