Taylor Swift's "Look What You Made Me Do" blasted to the top of the Billboard Hot 100 this week, ending a 16-week reign by the nation's song of the summer, "Despacito." But it's not exactly clear to most people how the country's hits — a source of both trendsetting and bragging rights across the music industry — are chosen.
How it's computed: According to Billboard, the Hot 100 chart comes together via a mix of three factors: song sales (35-45%), radio airplay (30-40%), and, crucially, online streaming (20-30%). Since 2014, Billboard has counted 1,500 plays of a song as one album sold, per the NYT.
Why it matters: Even though it makes up the smallest piece of the pie, Billboard's use of streaming has potentially the biggest impact on its charts — and the industry as a whole. It's perhaps most indicative of listeners' immediate tastes, which allows both zeitgeist-y artists like Taylor Swift to fly to the top spot and larger labels to attempt to game the system to their advantage.