In April 2014, an unreleased Aphex Twin album from two decades earlier turned up on Discogs, a crowdsourced music database and marketplace favored among record collectors. The price was an eye-popping $13,500. The sale of the record, one of reputedly five extant test pressings of the pioneering electronic musician’s Caustic Window LP, led to a funding campaign that finally brought a high-quality digital version of the record to a wider audience.

The saga helped punctuate the rise of Discogs, which has become something of a cross between Wikipedia and Amazon or eBay for the most passionate fans of physical music formats. Founded in November 2000 by then-Intel software engineer Kevin Lewandowski to catalog the dance music he enjoyed as a fan, the Oregon-based website recently celebrated its 15th birthday. To celebrate, Discogs has started releasing some of the proprietary information it has collected over the years about the music we trade and collect. Also today, Discogs is announcing that its new mobile app, currently in beta testing, will be available to all iOs users on February 29 via the Apple Store.

-=-=-=-Sales in the Discogs marketplace rose 31% last year to about 6.6 million units, according to a 2015 year-in-review report provided exclusively to Pitchfork. That includes roughly 5.4 million vinyl records, an increase of 31% over 2014. CDs, which recently earned a spirited defense in Rolling Stone, got the biggest bump, climbing 38% to 1.1 million, followed by the cassette, which advanced 37% to 90,173 units sold. Cassettes also saw the fastest growth in terms of new listings on Discogs, increasing almost 39% from 2014 with more than 93,000 releases added to the database in 2015. (It’s worth noting Discogs’ data is proprietary and couldn’t be independently verified.)

By comparison, sales of new vinyl albums rose 30% last year to 11.9 million copies, according to Nielsen Music, versus an 11% decline for CDs to less than 126 million copies. (Nielsen’s annual report didn’t break out sales of cassettes.)

Overall, more than $95 million in sales took place on the Discogs marketplace last year, according to the company.

Discogs also shared some quirkier stats. A tough-to-find edition of hardcore band Judge’s Chung King Can Suck It, which in March became the most expensive record ever sold on the site when it went for $5,958.36, ended the year still in the top spot. A close second came in June, when William Powell’s Northern Soul rarity "Heartache Souvenirs" sold for $5,449, according to the report. Also among the priciest Discogs items purchased is a copy of the Smiths’ first single, "Hand in Glove," with a negative version of the original sleeve; only five copies were reputedly made, and this one sold in November for more than $3,000.

The most collected titles overall on Discogs last year included some of the best-selling records of all time. Leading the way was Fleetwood Mac’s Rumours, followed by Michael Jackson’s Thriller. Beyond that, though, were more recent, vinyl-friendly releases such as Daft Punk’s Random Access Memories, Jack White’s Lazaretto, and Sufjan Stevens’ Carrie & Lowell. These records were some of the best-selling vinyl releases of the last few years overall, so in this sense Discogs sales trends mirror the rest of the industry.