The Billboard Hot 100 is the best-known singles chart in the United States, and a new number one is still big news. But the chart is not a simple count of plays or purchases. It combines several kinds of data, each measured in its own way, into a single ranking. Understanding that mix explains a lot of chart headlines, from surprise debuts to songs that linger for months.

Three pools of data

According to Billboard's own charts legend, the Hot 100 is one of a group of charts that mix three types of data: sales, radio airplay and streaming. Billboard explains the reasoning plainly: a purchase or a stream is a strong vote of popularity, but singles also do a job beyond selling, which is to get played on the radio and streamed widely.

Sales data for Billboard's charts is compiled by Luminate from a large universe of retailers, including digital downloads. Radio data comes from Mediabase, which electronically monitors stations in many U.S. markets and identifies songs by audio fingerprint, with the information provided to Billboard by Luminate. Streaming data covers on-demand audio and video streams as well as programmed streams on leading services.

The tracking week

Billboard's legend states that charts generally reflect sales and airplay between Friday and Thursday of a given week. That is why most major releases come out on Fridays: a song released on a Friday gets a full tracking week to accumulate streams and sales. Charts are refreshed on Billboard's website on Tuesdays, and each chart carries the date of the magazine issue in which it appears, which is later than the tracking week itself. This dating system confuses many readers, who see a chart dated a week or more in the future.

Why debuts can be so big

When a major artist releases an album, many of its songs can appear on the Hot 100 at the same time, because streams of album tracks count toward each individual song. In the streaming era, a heavily anticipated album can place a large number of songs on the chart in its first week. Many of those tracks then fall quickly as listeners settle on favourites, while one or two keep climbing through radio play.

Radio tends to move more slowly than streaming. A song that debuts high on the back of streams may keep a strong position for months if it is picked up by radio formats, while a song driven only by first-week streaming excitement can drop sharply.

Recurrent rules

To keep the chart from filling up with old hits, Billboard applies recurrent rules, which move declining songs off certain charts after a set period once they fall below a particular rank. The details differ by chart and are published in the charts legend. These rules explain why a song that is still popular can disappear from a chart; it has not stopped being played, it has simply been moved to recurrent status under the chart's rules.

Chart symbols and awards

The legend also defines the symbols you see beside songs. A bullet marks titles with the greatest weekly gains in overall points. Other awards highlight the biggest gains in airplay, streaming or sales. These can be useful signals of momentum, especially for songs below the top ten.

Global and genre charts

The Hot 100 is a U.S. chart. Billboard also publishes global charts and many genre charts, and a song can top a genre chart without reaching the upper part of the Hot 100. Headlines sometimes blur these differences. "Number one" should always come with the name of the chart.

Why rules change

Billboard updates its methodology from time to time, for example in how it weighs different kinds of streams or how it treats bundles and special editions. Changes like these can affect how songs perform and make historical comparisons tricky. When an article compares a current song with one from decades ago, remember that the chart has been measuring different things in different eras. Sales-driven charts from the past and streaming-driven charts today are related, but they are not identical scoreboards.

Reading chart news

A few questions help when reading chart coverage. Which chart is it: the Hot 100, a genre chart or a global chart? Which tracking week does it cover, and when was the song released within that week? What drove the position: streaming, radio, sales or a combination? And is the record being described a record on the current methodology, or across the chart's entire history?

The bottom line

The Hot 100 is a weekly snapshot of how a song is performing across listening, buying and radio in the United States. It rewards both the sudden burst of a big release and the slow build of a radio hit. Knowing how the data comes together makes it easier to see which kind of success a chart headline is really describing.

Sources