Billboard Year-End charts are a cumulative measure of a single or album's performance in the United States, based upon the Billboardmagazine charts during any given chart year. Billboard's "chart year" runs from the first Billboard "week" of December to the final week in November, but because the Billboard week is dated in advance of publication, the last calendar week for which sales are counted is usually the third week in November. This altered calendar allows for Billboard to calculate year-end charts and release them in time for its final print issue in the last week of December. Due to this methodology, albums at the peak of their popularity at the time of the November/December chart-year cutoff many times end up ranked lower than one would expect on a year-end tally, yet are ranked on the following year's chart as well, as their cumulative points are split between the two chart years. Prior to incorporating chart data from Nielsen SoundScan, year-end charts were calculated by an inverse-point system based solely on a title's performance. Other factors including the total weeks a song spent on the chart and at its peak position were calculated into its year-end total. The same method was used for albums based on the Billboard 200, and songs appearing on the other charts. After Billboard began obtaining sales and airplay information from Nielsen SoundScan and Nielsen Broadcast Data Systems, the year-end charts are now calculated by a very straightforward cumulative total of yearlong sales points. This gives a more accurate picture of any given year's most popular titles, as an entry that hypothetically spent nine weeks at number one in the spring could possibly have earned fewer cumulative points than one spending six weeks at number three in January. Exceptions appeared to be in the 1980s as songs with chart runs were as high as they were as if they were in the chart for a whole year. Two examples are "Desire" by U2 and "How Can I Fall?" by Breathe, which both peaked at number 3 in November and December, respectively. "Desire" came in at number 56 in the 1988 year-end, then "How Can I Fall?" would take the number 27 spot in 1989, despite "Desire" appearing in only nine issues of the chart in the 1988 charting year, and "How Can I Fall?" having appeared in five in 1989. Songs are also not always placed as high in the Decade-End and All Time charts as they were in the Year-End. In the Decade-End, an example is in the 2008 year end which showed "No Air" by Jordin Sparks and Chris Brown and "I Kissed a Girl" by Katy Perry at numbers six and 14 respectively, but only "I Kissed a Girl" was in the decade-end of the two, at number 66. And another example is from the 1979 year end where "My Sharona" by The Knack is the number one song of 1979, but lower than "Hot Stuff" by Donna Summer in the all time chart. George Michael, The Beatles, Elton John and Elvis Presley are the only four artists to have ever achieved a year end number 1 hit twice.
''Billboard'' year-end number ones
; Pop Between 1959 and 1963 the chart was divided in a stereo chart and a mono chart and were named Best-Selling Stereophonic LPs and Best-Selling Monophonic LPs, Stereo Action Charts and Mono Action Charts, Action Albums—Stereophonic and Action Albums—Monophonic and Top LPs—Stereo and Top LPs—Monaural . ; R&B / Soul / Hip-hop ; Country
