The Billboard Hot 100 is the United States music industry standard singles popularity chart issued weekly by Billboard magazine. Chart rankings are based on airplay and sales; the tracking-week for sales begins on Monday and ends on Sunday; while the airplay tracking-week runs from Wednesday to Tuesday. A new chart is compiled and officially released to the public by Billboard on Thursday. Each chart is dated with the "week-ending" date of the Saturday after.
The limitations of the Hot 100 have become more pronounced over time. Since the Hot 100 was based on singles sales, as singles have themselves become a less common form of song release, the Hot 100's data represented a narrowing segment of sales until the December 1998 change in the ranking formula.
Few music historians believe that the Hot 100 has been a perfectly accurate gauge of the most popular songs for each week or year. For example, during the 1950s and 1960s, payola and other problems skewed the numbers in largely undetectable ways.
Further, the history of popular music shows nearly as many remarkable failures to chart as it does impressive charting histories. Certain artists (such as Pink Floyd and Led Zeppelin) had tremendous album sales while being oblivious to the weekly singles charts. Business changes in the industry also affect artists' statistical "records." Single releases were more frequent and steady, and were expected to have much shorter shelf lives in earlier decades, making direct historical comparisons somewhat specious. Of the sixteen singles to top the Billboard chart for more than ten weeks since 1955, just one was released before 1992. During the first forty years of the rock era, no song had ever debuted at number one; since a 1995 change in methodology, a dozen have.
Strategizing also plays a role. Numerous artists have taken deliberate steps to maximize their chart positions by such tactics as timing a single's debut to face the weakest possible competition, or massively discounting the price of singles to the point where each individual sale represented a financial loss. Meanwhile, other artists would deliberately withhold even their most marketable songs in order to boost album sales. Particularly in the 1990s, many of the most heavily played MTV and radio hits were unavailable for separate purchase. Because of such countervailing strategies, it cannot be said that a Hot 100 chart necessarily lists the country's 100 most popular or successful songs. Strategies like these were the main reason behind the December 1998 change in the charts.
Some critics have argued that an overemphasis on a limited number of singles has distorted record industry development efforts, and there are nearly as many critics of the Hot 100 as there are supporters. Certain of these criticisms, however, are becoming less and less germane as digital downloads have revitalized the concept of “singles sales.”
For good or ill, the Billboard charts have endured as the only widely-circulated published report on songs that have been popular across the United States over the last half-century. Competing publications such as Cash Box, Record World, and Radio & Records offered alternate charts, which sometimes differed widely. But even a perfect meld of all these charts could only provide scholars an imperfect overview of American popular music.