Ask a few musically aware people to guess which album by a group or duo has sold the most copies in any one week so far this year. I bet very few people will get it right. Here's the right answer: Zac Brown Band's Uncaged, which enters The Billboard 200 at #1 this week with sales of 234K copies. The runners-up (and your most likely wrong guesses) are Linkin Park's Living Things (223K), Maroon 5's Overexposed (222K), Van Halen's A Different Kind Of Truth (187) and One Direction's Up All Night (176K).

Uncaged sold more than 100K more copies than Frank Ocean's Channel Orange, which may be this year's most buzzed-about album. Uncaged even sold more digital copies than Channel Orange, which was an iTunes exclusive. Uncaged sold 139K digital copies (to rank #1 on Top Digital Albums). Channel Orange sold 128K digital copies. (More on Ocean in a minute.)

Luke Bryan's "Rain Is A Good Thing" this week become the 100th country song to sell 1 million digital copies. It's Bryan's fifth million-seller, which puts him in a tie with Jason Aldean for the most among male country solo artists. Taylor Swift accounts for 15 million-sellers, more than any other country artist. Carrie Underwood is in second place, with 10. Zac Brown Band is next in line, with seven.

Everybody knows Swift and Underwood, but Bryan has just broken wide open in the past year. His current album, Tailgates & Tanlines, has sold a healthy 1,246,000 copies. His current single, "Drunk On You," is his first top 20 hit on the Hot 100, after a couple of near-misses.

Carly Rae Jepsen's "Call Me Maybe" this week surpasses Nickelback's 2007 smash "Rockstar" to become the best-selling song by a Canadian act in digital history. "Call Me Maybe," which is in its fourth week at #1 on the Hot 100, has sold 4,067,000 copies. "Rockstar," which reached #6 in September 2007, has sold 4,019,000.

Jepsen is one of three female solo artists from Canada on Nielsen SoundScan's running list of the 200 best-selling songs in digital history. The others are Avril Lavigne, whose "Girlfriend" has sold 3,509,000 copies, and Nelly Furtado, whose "Promiscuous" (featuring Timbaland) has sold 2,833,000. Both of those songs also reached #1.

The biggest hits got significantly bigger in the first half of 2012, but there were slightly fewer medium-sized hits than in the same period last year. Two songs each sold more than 5 million copies in the first half of 2012. "Somebody That I Used To Know" by Gotye featuring Kimbra sold 5,501,000 copies in the first half. "We Are Young" by fun. featuring Janelle Monae sold 5,087,000. Never before in the digital era has one song, much less two, sold 5 million copies in any six month period. You have to go back to the pre-digital era to find the last song that sold 5 million or more copies in a six-month period. Elton John's "Candle In The Wind 1997" sold 8,111,000 copies in the last 14 weeks of 1997.