During the 1990s the chart was based collectively on each single's weekly physical sales figures and airplay on American radio stations.
The methodology for determining sales and airplay figures drastically changed with the chart dated November 30, 1991.
Instead of surveying retail stores and radio stations, sales data was now gathered by Soundscan via a collection of the number of barcode scans a record received while airplay was to be compiled by Broadcast Data Systems, which continuously monitored what songs were being played on radio.
[1] As the decade progressed, a growing trend in the music industry was to promote songs to radio without the release of a commercially available singles in an attempt by record companies to boost albums sales.
Santana's "Smooth" featuring Rob Thomas finished the decade and began the next with a 12-week run atop the Hot 100.