The change in formula has shaken up the chart considerably, with some songs debuting on the chart strictly with robust online sales and others making drastic leaps. In recent years, several songs have been able to achieve 80-to-90 position jumps in a single week as their digital components were made available at online music stores. Since 2006, the all-time record for the biggest single-week upward movement was broken nine times.
In the issue dated August 11, 2007, "Billboard" began incorporating weekly data from Streaming media and On-demand services into the Hot 100. The first two major companies to provide their statistics to Nielsen BDS on a weekly basis are AOL Music and Yahoo! Music, with more to follow in the future.
A growing trend in the early first decade of the 21st century was to issue a song as a "remix" that was so drastically different in structure and lyrical content from its original version that it was essentially a whole new song. Under normal circumstances, airplay points from a song’s album version, "radio" mix and/or dance music remix, etc. were all combined and factored into the song’s performance on the Hot 100, as the structure, lyrics and melody remained intact. Criticisms began when songs were being completely re-recorded to the point that they no longer resembled the original recording. The first such example of this scenario is Jennifer Lopez’ "I'm Real". Originally entering the Hot 100 in its album version, a "remix" was issued in the midst of its chart run that featured rapper Ja Rule. This new version proved to be far more popular than
the album version and the track was propelled to number one.
To address this issue, "Billboard" now separates airplay points from a song’s original version and its remix, if the remix is determined to be a "new song". Since administering this new chart rule, several songs have charted twice, normally credited as "Part 1" and "Part 2". The remix rule is still in place.
"Billboard", in an effort to allow the chart to remain as current as possible and to give proper representation to new and developing artists and tracks, has (since 1991) removed titles that have reached certain criteria regarding its current rank and number of weeks on the chart. Recurrent criteria have been modified several times and currently (as of 2010), a song is permanently moved to "recurrent status" if it has spent 20 weeks on the Hot 100 and fallen below position number 50. Exceptions are made to re-releases and sudden resurgence in popularity of tracks that have taken a very long time to gain mainstream success. These rare cases are handled on a case-by-case basis and ultimately determined by "Billboard"’s chart managers and staff.
The most notable exception to the recurrent entry policy applies to holiday-themed releases, which are commonly reissued year after year in anticipation of Christmas purchasing. After its initial chart run, a holiday entry cannot re-enter the Hot 100 in subsequent years.
"Billboard"'s "chart year" runs from the first week of December to the final week in November. This altered calendar allows for "Billboard" to calculate year-end charts and release them in time for its final print issue on the last week of December. Prior to Nielsen SoundScan, year-end singles charts were calculated by an inverse-point system based solely on a song’s performance on the Hot 100 (for example, a song would be given one point for a week spent at position 100, two points for a week spent at position ninety-nine and so forth, up to 100 points for each week spent at number one). Other factors including the total weeks a song spent on the chart and at its peak position were calculated into its year-end total.
After "Billboard" began obtaining sales and airplay information from Nielsen SoundScan, the year-end charts are now calculated by a very straightforward cumulative total of yearlong sales and airplay points. This gives a more accurate picture of any given year’s most popular tracks, as a song that hypothetically spent nine weeks at number one in March could possibly have earned fewer cumulative points than a song that spent six weeks at number three in January. Songs at the peak of their popularity at the time of the November/December chart-year cutoff many times end up ranked on the following year's chart as well, as their cumulative points are split between the two chart-years, but often are ranked lower than they would have been had the peak occurred in a single year.
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, nineteen songs 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.”
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", "Radio & Records" and most recently "Mediabase" have offered alternate charts, which sometimes differed widely.
The Hot 100 served for many years as the data source for the weekly radio countdown show "American Top 40". This relationship ended on November 30, 1991, as "American Top 40" started using the airplay-only side of the Hot 100 (then called Top 40 Radio Monitor). The ongoing splintering of Top 40 radio in the early 1990s led stations to lean into specific formats, meaning that practically no station would play the wide array of genres that typically composed each weekly Hot 100 chart.