RIN3GUY said:I would like to know the month and year they started doing this. It would affect the way I look at my Whitburn books. I would also like to know how much weight was given to airplay vs. sales.
The October 11, 1980 issue of Billboard is the first where the Hot 100 chart mentions airplay as part of the formula. That squares with my memory as the change having taken place about the time I was transitioning from music to news.
In 1985, a column detailed the methodology in use at that time. Airplay was determined by the chart positions of records on the weekly surveys of 200 Top 40 stations that reported to Billboard each week. Sales was based on a points system applied to the 30 best-selling records at 200 individual (both mom & pop and chain) record stores around the country. A year later, the column included distributors in that mix, which brought wholesale back into the picture.
The exact ratio of airplay vs. sales isn't disclosed. However, given how far singles sales had fallen by 1985/86, and how tight playlists were, I'm surprised they could get a list of 100 records from radio playlists and the 30 best-selling records from 200 retailers.