On January 4, 1936, Billboard magazine published its first music hit parade and on July 20, 1940 the first Music Popularity Chart was calculated. Since 1958 the Hot 100 has been published, combining single sales and radio airplay.

Methodology of its charts
Currently, Billboard utilizes a system called Nielsen Soundscan to track sales of singles, albums, videos and DVDs. Essentially, it's a system that registers sales when the product is purchased at the cash register of SoundScan-enabled stores. Billboard also uses a system called Broadcast Data Systems, or BDS, which they own as a subsidiary, to track radio airplay. Each song has a musical "fingerprint" which, when played on a radio station that is contracted to use BDS, is detected. These detections are added up every week among all radio stations to determine airplay points. Arbitron statistics are also factored in to give "weight" to airplay based on audience size and time-of-day. Each of Billboard's charts use this basic formula. What separates the charts is what stations or stores each chart uses - each musical genre having a core audience or retail group. Each genre's department at Billboard is headed up by a chart manager, who makes these determinations. For many years, a song had to be commercially available as a single to be considered for any of Billboard's charts. At the time, instead of using SoundScan or BDS, Billboard obtained its data from manual reports filled out by radio stations and stores. In 1990, the country singles chart was the first chart to use SoundScan and BDS. They were followed by the Hot 100 and the R&B chart in 1991. Today, all of Billboard's charts use this technology. Before September 1995, singles were allowed to chart in the week they first went on sale based on airplay points alone. The policy was changed in September 1995 to only allow a single to debut after a full week of sales on combined sales and airplay points. This allowed several tracks to debut at number one. In December 1998, the policy was further modified to allow tracks to chart on the basis of airplay alone without a commercial release. This change was made to reflect the changing realities of the music business. Previous to this, several substantial radio and MTV hits had not appeared on the Billboard chart at all, because companies chose not to release them as standalone singles, in hopes that their unavailability would spur greater album sales. Not offering a popular song to the public as a single was unheard of before the 1970s. Among the many pre-1999 songs that had ended up in this Hot 100 limbo were Nirvana's "All Apologies," the Cardigans' "Lovefool," Smash Mouth's "Walking on the Sun," OMC's "How Bizarre," the Cowboy Junkies' "Sweet Jane," Harvey Danger's "Flagpole Sitta," Jamiroquai's "Virtual Insanity," Everclear's "Santa Monica," Stone Temple Pilots' "Interstate Love Song," Fastball's "The Way," the Smashing Pumpkins' "Disarm," Veruca Salt's "Seether," and The Cranberries' "Zombie," as well as numerous Green Day, Live, Offspring, No Doubt, Red Hot Chili Peppers, Mariah Carey, Alanis Morissette and Foo Fighters tracks. Starting in 2005, Billboard changed its methodology to allow paid digital downloads from digital music stores such as iTunes to chart with or without the help of radio airplay.

A variety of charts
Originally, Billboard had separate charts for different measures of popularity, including disk jockey playings, juke box playings, and best selling records in stores. There was also a composite standing chart compiled by combining those, which gradually grew to become a top 100, the ancestor of the current Hot 100 chart. The juke box chart ceased publication after the June 17, 1957 issue, the disk jockey chart, after the July 28, 1958 issue, and the best seller chart, after the October 13, 1958 issue. The July 28, 1958 issue was also the last issue in which the composite chart was called the Top 100; the following week was the start of the Hot 100 title. Currently, Billboard has many different charts with the Hot 100 and Billboard 200 being the most famous. Billboard also has charts for the following music styles: rock, country, dance, bluegrass, jazz, classical, R&B, rap, electronic, pop, latin, christian music, comedy albums, and even for ringtones for cell phones.

At year's end
At the end of each year, Billboard tallies the results of all of its charts, and the top single/album/artist(s) in each of those charts is awarded in the form of the annual Billboard Music Awards, held in December. The results are also published in Billboard's year-end issue, and heard on year-end edition of its American Top 40 and American Country Countdown radio broadcasts. The year-end charts cover a period from the first week of December of the previous year to the last week of November of the respective year.

Airplay charts
Although the airplay charts are featured in Billboard, it can also be seen in its sister publication R&R, which also publishes the playlists for the stations that are monitored by BDS. Prior to this, the listings were featured in their predecessor Billboard Radio Monitor, which was a spin off weekly publication from Billboard. The magazine, originally called "Airplay Monitor," published its first issue on January 10, 1993 until its last issue on July 14, 2006, when VNU purchased rival trade Radio & Records and combined the two trades the following August