How does a song become number one?

OMI’s reggae-influenced and incredibly addictive song “Cheerleader” continues its two-week reign as the number one song in America. This year, the number one club is very exclusive. So far, only 7 songs have occupied the number one slot in America—one fewer than this time last year, and half as many as there had been at this time in 1990.

That’s because even though the music industry’s method of promoting, selling, and marketing music has completely transformed in the last 25 years, the way a number one song is decided is still really similar. The number one spot is elusive, it’s so easy to nearly miss it, and it carries a kind of prestige that no artist can deny wanting. How could you not want your song to be America’s absolute favorite song?

But how does a song become number one? Who decides? And Why?

The song has to be good (and accessible)

The first step to snagging a number one song is, well, writing and producing a really good song. “Wait,” you say, “but “Cheerleader” is the number one song in the country right now and it’s awful! Listening to that song makes me feel like my eardrums are being coated in an awful tar that will never leave me alone.”

You’re not alone! Many people hate “Cheerleader,” just like many people hated “Fancy” and “Blurred Lines,” and almost every other number one song of all time.

That’s because making a “good” number one song is not necessarily the same as making a “good” song in general. It’s not about artistry (though sometimes artistry does hit number one). It’s about popularity. And not long-term popularity. But popularity right here, right now.

Even making a timeless, great song doesn’t necessarily mean that your song will perform well on the Hot 100 chart. Take Nirvana’s “Smells Like Teen Spirit”— which Polygraph recently found to be the most played song of the ’90s on Spotify—as an example. “Smells Like Teen Spirit” was never a number one song. It wasn’t even in the Top 5.

What determines whether a song will become number one isn’t how popular it is on a grand scale, but how able it is to permeate the human consciousness and become popular in a very particular instant. What makes a song “good enough” to be number one, then, isn’t it’s quality of performance, but it’s quality of repeat. A great number one song can be played over and over and over again.

And those plays, circularly, are what make it the number one song in the country.

Every week counts independently

The Billboard Hot 100 chart is calculated on a weekly basis. For a long time, the Billboard charts counted from Monday to Sunday as a standard week. But starting in July 2015, when new music began to standardly come out on Fridays, Billboard has been tracking a single week from Friday to Thursday. At the end of the week, your numbers reset. (And we find out what the number one song is every Tuesday. Are you keeping up?)

So there’s a huge benefit to releasing song or album on the standard release day (Friday); it helps to take advantage of the way the system counts sales. Release day matters a lot, for the Hot 200 albums chart as well, not just for singles. Take Beyoncé’s 2013 self-titled surprise album. Because she released it on a Friday, and at that time the week in music sales was counted from Monday to Sunday, her “first week” of sales only included that Friday, Saturday, and Sunday. She didn’t get the “instant million” recognition that Taylor Swift did 1989. The playing ground was not equal.

Now that doesn’t matter much for an artist like Beyoncé—she’s doing fine. But it certainly matters for an artist trying to make an impact, trying to get attention for their first song.

To be clear, this doesn’t mean that your only chance to have a number one single is immediately after it comes out. Some songs peak much later. We call those “sleeper hits”—songs like Iggy Azalea’s “Fancy,” for example. A song can peak because of a really great music video, or its inclusion in something else popular (like a movie trailer). For example, N.W.A. finally snagged their first top 40 hit in the wake of the release of the movie Straight Outta Compton almost 30 years after its release

But every week on Friday, the counter clocks reset, and a song has to prove itself the best in the country all over again.

The first factor in number one calculations: sales

For most artists, selling songs is an important part of the revenue stream. Touring makes money, but how many albums you’ve sold influences how big your tour is—it’s a way to measure popularity. Even if a song never charts, selling a lot of albums can help an artist get a second album promoted, as well as establish a base of fans who can support a full tour.

The number of albums sold is determined by Nielsen Soundscan, a service that monitors how many albums an artist sells both digitally and physically. According to Nielsen’s site, the organization compiles data from more than 39,000 retail outlets globally every week, and then reports the findings to Billboard to use in a specially concocted ratio to pick the Top 100.

In the calculations for number one, sales only play a small role. According to Billboard, sales make up somewhere between 35-45% of the ratio that determines how well a song does on the charts. But if a single has massive sale numbers, that alone could bump it into the Top 40.

But no one buys music. What about streaming?

Great point! Fewer and fewer people are choosing to spend money on songs. Instead, they’re streaming them on their computers. Billboard and Nielsen recognized this, and took great efforts to include it in the formula.

In February 2005, Billboard began to include digital sales of albums from digital retailers like iTunes and Rhapsody. The magazine also separately tracked which songs were doing well digitally on a new chart called Hot Digital Tracks.

In 2007, the system evolved to include streaming songs from platforms like Yahoo Music and AOL Music. Since then, the charts have been brought up to date by including platforms like Spotify and Apple Music, in addition to views from YouTube—with one video play counting as a song play.

Ultimately, though, streaming only makes up a small fraction (20-30%) of the formula used to determine the ranking of songs in America.

What matters more than streaming? Radio

It’s tempting to discount radio as something that only olds listen to. Who doesn’t just make Spotify playlists or listen to the “radio” on Pandora—one that’s specifically curated for them? Turns out, almost everyone. Radio has, for decades, been the most stable part of the music industry in terms of maintaining listeners.

According to a 2013 Pew Research Center report on audio listening in the US, almost 92% of the listening public listens to AM/FM radio. That percentage hasn’t changed much over the last 10 years, even with the advent of the internet. Some of the influence of radio might be waning, but for now, it takes a big slice of the listening pie, and a big percentage of the number one calculations.

The biggest AM/FM radio company in America, iHeart Radio, says people tune in to the radio eight times per day. According to the Pew Research Center, people spend more time listening to the radio than they do surfing the internet. And radio plays take care of the rest of the counting ratio with 30-40%.

So once a song is pretty popular, it becomes easier for that song (and sometimes the artist attached to it) to get airplay on radio stations, including Top 40 radio, and start a steady climb toward the top of the charts.

Getting into the Top 40 might take luck, but getting the number one song in America takes more than that—it takes a precise confluence of every form of viral behavior all at once. People have to buy the song, they have to hear it on the radio and watch the video on YouTube. It has to, simply, be a hit.

This week, that hit is “Cheerleader”, a song that hit number one in Sweden last November, number one in France in April, and number one in the U.S. in late July. Since then, it’s stayed in that number one slot for six weeks (with a one week interruption for the Weeknd’s “Can’t Feel My Face.”) Maybe “Cheerleader” is a hit because of its summery, reggae-inspired vibes, so similar to last year’s “Rude” by Magic!. Or maybe it’s number one because it’s impossible to escape, and people just really love it. Even if you don’t.