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.Currently, Billboard utilizes a system called Nielsen Sound Scan to track sales of singles, albums, videos and DVDs.Essentially, it's a system that registers sales when products are purchased from Sound Scan-enabled stores.Billboard is considered the foremost worldwide authority worldwide in music charts, and the rankings have gained a following among the general public.On January 4, 1936, Billboard magazine published its first music hitparade.Arguably, the NME chart was still the most recognised chart, and had the advantage of widespread exposure due to its use by Radio Luxembourg.Throughout the sixties, the various different charts vied for public recognition, leading to some historical anomalies for example, The Beatles' second single "Please Please Me" was a number one on most charts, but not in Record Retailer.
According to the 50th Anniversary issue of Billboard, prior to the official implementation of Nielsen Sound Scan tracking in November 1991, many radio stations and retail stores removed songs from their manual reports after the associated record labels stopped promoting a particular single.
The chart, at first a top 12, was the creation of the paper's advertising manager, Percy Dickins, who compiled it by telephoning around 20 major record stores and aggregating their sales reports.
He would continue to personally oversee the compilation of the chart well into the 1960s.
The first Music Popularity Chart was calculated in July, 1940.
A variety of song charts followed, which were eventually consolidated into the Hot 100 by mid-1958.