The collaboration dethrones Eminem and Rihanna's 'The Monster' after a four-week reign. Plus, Katy Perry gallops into the top 10 with 'Dark Horse,' featuring Juicy J

After a four-week wait at No. 2, Pitbull and Ke$ha climb to the top of the Billboard Hot 100 with "Timber." The new leader had held at the runner-up spot while Eminem and featured artist Rihanna reigned for four frames with "The Monster," which this week slips to No. 3.

Meanwhile, Katy Perry charges into the top 10 with "Dark Horse," featuring Juicy J.

As we do each Wednesday, let's dig deeper into the numbers behind the Hot 100's top 10.

With the coronation of "Timber," Pitbull collects his second Hot 100 No. 1. "Give Me Everything," featuring Ne-Yo, Afrojack and Nayer, topped the July 9, 2011, ranking. Ke$ha claims her third Hot 100 No. 1; her debut single "TiK ToK" ruled for nine weeks in 2010, while "We R Who We R" crowned the Nov. 13, 2010, tally.

"Timber" spends a fourth week atop the Digital Songs chart, with 301,000 downloads sold (down 32%), according to Nielsen SoundScan. As previously reported, only three songs on the 50-position Digital Songs chart sport an increase in sales over the prior week, following last week's hefty sales week following Christmas. The week after Christmas normally brings a surge in digital song sales, thanks to the redemption of newly-acquired digital gift cards. (Total song sales for the week ending Jan. 5 were down by 29%; in the previous week, they soared by 98%.)

"Timber" adds the Hot 100's top Streaming Gainer award, vaulting 6-2 on Streaming Songs with a 21% gain to 5.3 million U.S. streams, according to Nielsen BDS. It likewise lifts 6-2 on the subscription services-based On-Demand Songs chart (1.8 million, up 40%).

On Radio Songs, "Timber" returns to its No. 5 peak, from No. 6, with an 8% gain to 109 million all-format audience impressions, according to BDS. (Chart historians, take note: as of this week, Radio Songs becomes the chart's name across all Billboard platforms; it previously went by Hot 100 Airplay in Billboard magazine and on billboard.biz. The tweak, thus, better streamlines the names of the Hot 100's three main component charts: Radio Songs, Digital Songs and Streaming Songs. Additionally, Digital Songs drops the "Hot" at the beginning of its name in print and on billboard.biz. The prefix "Hot" will now be reserved solely for the sales/airplay/streaming hybrid charts, which mirror the Hot 100's methodology. Adding "Hot" as of this week are Dance/Electronic Songs, R&B Songs, Rap Songs, Christian Songs and Gospel Songs.)

"Timber" concurrently takes over atop Hot Rap Songs, which "Monster" had led for nine weeks.

Below "Timber" on the Hot 100, OneRepublic's "Counting Stars" rises to No. 2 after four weeks at No. 3. With the advance, OneRepublic ties its best chart rank: its debut hit, "Apologize" (credited to Timbaland featuring OneRepublic), peaked at No. 2 for four weeks in late 2007.

"Stars" holds at No. 2 on Radio Songs for a fourth week (139 million, up 7%) and at No. 3 on Digital Songs (237,000, down 42%) and rebounds 10-7 on Streaming Songs (4.1 million, up 7%).

In terms of overall Hot 100 chart points, "Timber" wins the top spot by a 9% margin over "Stars."

As it vacates the Hot 100's summit, "Monster" continues leading Radio Songs for a fifth week (145 million, up 6%). It drops 2-5 on Digital Songs (220,000, down 49%) and 5-6 on Streaming Songs (4.3 million, down 9%). "Monster" spends a 10th week at No. 1 on the Hot R&B/Hip-Hop Songs chart.

Rounding out the Hot 100's top five, Lorde's former nine-week Hot 100 No. 1 "Royals" stays at No. 4 (and leads Hot Rock Songs for a 19th week) and A Great Big World and Christina Aguilera's "Say Something" keeps at No. 5.

Katy Perry crashes the Hot 100's top 10 with "Dark Horse," featuring Juicy J (11-6), the third single from her former Billboard 200 No. 1 album "PRISM." Lead track "Roar" spent two weeks at No. 1, while follow-up "Unconditionally" reached No. 14 (and this week slides 20-29). "Horse," which marks Perry's lucky 13th Hot 100 top 10, trots to the top 10 as the Hot 100's top Airplay Gainer, bounding 28-18 on Radio Songs (52 million, up 28%). It jumps 7-4 on Digital Songs (229,000, down 20%), returning to its peak position logged upon its Oct. 5, 2013, debut as a "PRISM" preview track. "Horse" hits the Streaming Songs top 10 (14-10), swelling by 26% to 3.6 million.

Perry's last album, 2010's fellow Billboard 200-topping "Teenage Dream," yielded five Hot 100 No. 1s, tying Michael Jackson's "Bad" (1987-88) for the most leaders from a single set. Reissued as "Teenage Dream: The Complete Confection," the new version of the album generated another Hot 100 ruler, "Part of Me," in 2012.

Closing out the Hot 100's top 10, Passenger's "Let Her Go" holds at its No. 7 peak; Avicii's No. 4 hit "Wake Me Up!" rebounds 10-8 (and commands Hot Dance/Electronic Songs for a record-extending 18th week); Miley Cyrus' former three-week Hot 100 No. 1 "Wrecking Ball" returns to the top 10 (12-9) and passes her own "We Can't Stop" for the longest reign over Streaming Songs (12 weeks, totaled nonconsecutively; it rises 2-1 on the list, up by 10% to 7.6 million); and Imagine Dragons' "Demons" slips from its No. 6 Hot 100 peak to No. 10.

Visit Billboard.com tomorrow (Jan. 9), when all rankings, including the Hot 100 in its entirety and Digital Songs, Radio Songs, Streaming Songs and On-Demand Songs, will refresh, as they do each Thursday. The latest charts will also appear in the next issue of Billboard magazine (on sale on Friday, Jan. 10).