Most of the year-end charts in our special online section  represent aggregated sales or radio airplay (audience impressions or total plays) for each artist and title from the weekly charts on which they appeared during the 2009 chart year (December 2008 - November 2009).
The sales totals are based on data compiled by Nielsen SoundScan, with radio airplay measured by Nielsen BDS.
Sales or airplay registered before or after a title's chart run are not considered in these standings. That detail, and the December-November time period, account for some of the differences between these lists and the calendar-year recaps that are compiled independently by either SoundScan or BDS.
The Billboard Hot 100 and Hot R&B/Hip-Hop Songs categories reflect accumulated radio and sales points, based specifically on BDS and Nielsen SoundScan, respectively. For the Hot 100, points from streamed music on AOL and Yahoo! also shape the standings.
For the top, country and R&B/hip-hop categories that combine data from album charts and singles charts, formulas have been weighted so that the sales units tallied on The Billboard 200, Top Country Albums and Top R&B/Hip-Hop Albums, respectively, have parity with the specific chart points that construct each week's Billboard Hot 100, Hot Country Songs and Hot R&B/Hip-Hop Songs.
The Dance Club Play rankings are based on an inverse point system, with titles collecting points based on rank for each week they were on the chart.
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