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.