Not all that long ago, conventional wisdom held that the music industry was fracturing so much, and so quickly, that there wouldn't be many monster hits anymore.

But perhaps you've heard of a singer named Adele.

Her album 25 -- which was only released on Nov. 20 — ruled the 2015 charts by far, according to Nielsen Music, which released its detailed year-end report on Wednesday.

Over 7.4 million units of 25 were sold during the last six weeks of the year — it was easily the top-selling digital and physical album of 2015. 25 accounted for over 3 percent of every single album sold during 2015 and a whopping 16 percent of the albums sold between Nov. 20 and Dec. 31. (By comparison, Taylor Swift's 1989, which was 2015's second-biggest hit album, represented just under 2 million units for the entire year.)

25's first-week sales were also the stuff of instant industry legend: With over 3.3 million units sold during its initial release week, Adele easily slid past the former record held by boy band *NSYNC, whose No Strings Attached sold over 2.4 million units in its first week on sale back in 2000.

Adele's enormous success also bucks the year's other major trend: More and more music fans' listening preferences are shifting to streaming. 25 was not made available on any streaming platforms, including Spotify or Apple Music (her singles "Hello" and "When We Were Young" were streamed nearly a billion times on YouTube and Vevo).

Before 25 was released, it seemed like the biggest story to emerge from this Nielsen year-end report would be that upward growth in streaming. Compared to 2014, audio streaming was up 83 percent, while video streaming increased 102 percent. (However, as Billboard reported in July when Nielsen released its mid-year report, the company improved its data-capturing capabilities in 2015, so it's unclear how much of last year's surge is due to a change in consumer habits.)

Looking at the opposite end of the audiophile spectrum, vinyl sales also continued their upward march, in a nearly 30 percent increase over 2014. Nearly 12 million vinyl units sold this year, making 2015 the tenth straight year of growth. Also notably, over 45 percent of vinyl sales came from independent record stores, and nearly 18 percent of all physical rock albums sales in 2015 were vinyl LPs.

That last bit of data leads to another intriguing takeaway from the 2015 Nielsen report: There seemed to be a significant splinter in what kinds of musicians do best in which format — whether with physical CD sales, digital sales, streaming or vinyl.

Looking past Adele and Taylor Swift, mainstream country and pop artists including Luke Bryan and Sam Smith were the top sellers in CDs, while Drake and Justin Bieber were among the biggest sellers of digital albums.

However, the songs with the top total on-demand streams (of audio and video combined) in 2015 were quite different: Fetty Wap's "Trap Queen" led the way, followed by Silento's "Watch Me (Whip/Nae Nae)," Mark Ronson's "Uptown Funk!" featuring Bruno Mars, Wiz Khalifa's "See You Again" featuring Charlie Puth and The Weeknd's "The Hills."

And by significant contrast, the top five in vinyl sales, after Adele and Taylor Swift, included artists who have been household names for decades: Pink Floyd, The Beatles and Miles Davis.

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• The Chart Show: Best of 2015
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