Back in the day, the album charts were compiled by having some guy call around to a bunch of record stores to get a report on what records were selling. In 1991, the SoundScan system was introduced, a much, much more accurate gauge of sales.
Then came the internet. When music started being sold online (I’m looking at you, iTunes), chart compilation data had to include downloads. This led to a new metric called “Track Equivalent Albums” (TEAs) was introduced. This is calculated by adding up all of the song sales from an album and dividing by 10. That means every ten downloads from the same album is the equivalent of the sale of one album, either a physical unit or a digital one.
But with physical sales and paid downloads on the decline, album charts rely more and more on streaming statistics. This results in some weird twists.
Take, for example, last week’s American Billboard charts. The number one record was SOS by SZA. In the whole of the United States with its 330 million people, it sold exactly 778 copies. That is not a typo. SOS was purchased–as a physical copy or paid download–by just 778 people. But once you figure in all the streams the album generated, you get an equivalent of 123,000 units sold. That was better than anything else, hence the number one finish.
Compare that to the number two album, Midnights from Taylor Swift. It sold 63,000 CDs/LPs/paid downloads.