Perhaps Rob Base and DJ EZ Rock were right: It takes two to make a thing go right.

It’s still early days, but for all of 2014, the No. 1 slot on the  Billboard Hot 100 has been ruled by co-ed collaborations instead of solo artists.

Eminem’s “The Monster,” featuring Rihanna, ushered in the New Year at No. 1, only to be replaced by Pitbull’s “Timber,” featuring Ke$ha, and, for the last three weeks, Katy Perry’s “Dark Horse,” featuring Juicy J.

Also residing comfortably in the top 10 are Beyonce and Jay Z’s “Drunk in Love,” “A Great Big World’s “Say Something,” featuring Christina Aguilera, and Jason Derulo’s “Talk Dirty,” featuring 2 Chainz.

Such pairings aren’t new—during Top 40’s most recent rhythmic-leaning phase that lasted from 2010 to 2012, it seemed like almost every pop song had a hip hop artist joining in for an obligatory rap verse or two—but a growing number of collaborations have been reaching the summit.

In 2013, only 3 of the 13 songs that topped the Billboard Hot 100 were collaborations. Last year, nearly half —five— of the 11 songs that reached No. 1 were pairings featuring artists who don’t normally record together. So far in 2014, it’s been every song.

Is this all a coincidence or have we now entered an era where it takes an “event” record to top the charts?

In almost all cases, the whole is greater than the sum of the parts. A song featuring Pitbull and Ke$ha appeals to a both of the acts’ fans, increasing the reach for the song. With Eminem and Rihanna’s “The Monster,” fans get a sequel of sorts to “Love The Way You Lie,” the pair’s 20110 smash, and the labels get a strong marketing hook as they can push the reunited pair. Same with Beyonce and Jay Z’s “Drunk in Love.”

In some cases, such as last year’s No. 1, Pink’s “Just Give Me A Reason,” featuring fun.’s Nate Ruess, the narrative of the song needs two people to tell the tale. In others, such as “Dark Horse,” the Juicy J’s rap provides a counterbalance to Perry’s singing. Last year’s “Hold On, We’re Going Home” from Drake, featuring Majid Jordan, helped bring Jordan to a bigger audience.

They don’t always work. “Can’t Remember to Forget You,” Shakira’s much-hyped pairing with Rihanna, is already falling back down the Hot 100 after only four weeks. Zedd’s “Stay The Night,” featuring Paramore’s Haley Williams, peaked at No. 18.

Clearly, solo acts don’t always need a partner to reach the top: Katy Perry got there just fine by herself with “Roar,” and Pharrell’s “Happy” looks good to be the next chart topper. Bear in mind, that comes after Pharrell spent much of last year in the Top 10 as a featured artist on Robin Thicke’s “Blurred Lines,” which spent 12 weeks at No. 1, and Daft Punk’s “Get Lucky,” both of which greatly increased his visibility, helping pave the way for “Happy’s” success.

Maybe one really is the loneliest number.