Pentatonix perform during the 83rd Rockefeller Center Tree Lighting

Pentatonix perform during the 83rd Rockefeller Center Tree Lighting on Dec. 2, 2015 in New York City. 

Theo Wargo/Getty Images

A cappella quintet Pentatonix is the top musical act in the U.S., lifting from No. 2 to No. 1 for its first week atop the Billboard Artist 100 chart (dated Jan. 7, 2017).

The Artist 100 measures artist activity across Billboard's most influential charts, including the Billboard Hot 100, Top Album Sales and the Social 50. The Artist 100 (which launched in July 2014) blends data measuring album and track sales, radio airplay, streaming and social media fan interaction to provide a weekly multi-dimensional ranking of artist popularity.

Pentatonix commands the Artist 100 for the first time as its holiday LP A Pentatonix Christmas likewise lifts 2-1 (in its ninth chart week) on both the Billboard 200 (with 206,000 equivalent album units, up 32 percent, in the week ending Dec. 22, according to Nielsen Music) and Top Album Sales (185,000 copies sold, up 33 percent). Album sales account for the greatest share of the group's Artist 100 chart points (65 percent).

Pentatonix is the first a cappella act to top the Artist 100, as well as the first pop group to reign in more than two years, since Maroon 5 (Sept. 27, 2014).

Rounding out the Artist 100's top five, The Weeknd rebounds 3-2 (after logging 10 nonconsecutive weeks at No. 1), as his single "Starboy," featuring Daft Punk, hits the top of the Hot 100; Bruno Mars (4-3) and Drake (5-4) also each rise a rung on the Artist 100; and J. Cole drops to No. 5 after his first week at No. 1, as he was powered a week ago by the chart debut of his new album, 4 Your Eyez Only.

Check out this week's entire Artist 100 here.