Whiteboard
Whiteboards became commercially available in the early 1960s, but did not become widely used until 30 years later. Early whiteboards needed to be wiped with a damp cloth and markers had a tendency to leave marks behind, even after erasing the board. Dry-erase markers for whiteboards were invented in 1975.
Record chart
According to Joel Whitburn, the American trade publication "Billboard" introduced the Hot 100 on August 4, 1958. This was the first chart in the US to "fully integrate the hottest-selling and most-played pop singles." From 1958 until 1991, "Billboard" compiled the chart from playlists reported by radio stations, and surveys of retail sales outlets. Before 1958, several charts were published, including "Best Sellers in Stores", "Most Played by Jockeys" (later revived under the name Hot 100 Airplay), and "Most Played in Juke Boxes", and, in later collations of chart hits, the record's highest placing in any of those charts was usually reported. On November 30, 1991, "Billboard" introduced a new method of determining the Hot 100, "by a combination of actual radio airplay monitored electronically by Nielsen Broadcast Data Systems (BDS), additional playlists from small-market stations, and actual point-of-sale information provided by Nielsen SoundScan." Until 1998, any songs placed on the chart had to be physically available as a single. The Hot 100 continues to be published.