As Discogs, the online vinyl and CD marketplace, celebrates its 15th anniversary, Billboard estimates that the site has supported $43.5 million in transactions so far this year.

That's based on proprietary data supplied by the site to Billboard. (Note: Because of its provenance, the data could not be independently confirmed.) According to Ron Rich, who oversees marketing for the site, so far this year about 2.5 million records have been sold among the buyers and sellers who trade on the site; as well as about 550,000 CDs and about 50,000 cassettes.

The site, founded by then-Intel programmer Kevin Lewandowski in 2000, started life as a hobby catalog for Lewandowsky's favorite genre, electronic music. “He liked the album art and the sound that vinyl provided, but he really liked a lot of underground music that was tough to find,” Rich says. Lewandowski started with his collection of 250 pieces, working nights and weekends to automatically cross-link artists, releases and labels on a scrappy Pentium II server in his closet, according to Rich. From there, the site slowly became a user-generated, wiki-like database.

“The reason it was focused on electronic music was because it was Kevin’s own collection that started the site….[He] started out to catalog all of the techno and drum ’n’ bass music in the world." The site's first transaction "was a techno album from SP-23 called This is Trance,” Rich says.

Now the operators are on a quest to catalog every piece of music in the world. In 2005 it added the now-central marketplace before expanding into other genres. Based in Beaverton, Oreg., Discogs now has an office in the Netherlands and employs about 40 people in total -- about half of them are developers, while the other half of the company is a community support team, Rich says.

The exponential growth of the site can be attributed at least in part to the striking rise in popularity of vinyl over the past decade. Vinyl has grown to 9.1 million units sold in 2014, a total that will be topped this year -- sometime in the next week or two, as album sales so far this year already total 8.9 million. Based on Discog's data, the average price for a slab of vinyl stands at $14.55, with CDs at $11.70 and cassettes going for (a surprisingly high) $12.18. Vinyl is, unsurprisingly and by far, the most popular format traded on the site, accounting for about 79 percent of transactions. CDs account for 18 percent and cassettes 1.4 percent.

“According to Nielsen, vinyl sales were up 38 percent year over year,” Rich says. “We saw a similar boom with vinyl sales increasing 36 percent. Oddly enough, CDs saw the biggest boom, with a 43 percent increase year-over-year -- while Nielsen saw a 10 percent decline” in the format.

Average prices for vinyl are the highest since Discogs started tracking sales information in 2005; from 2005 through 2014, the average price per slab has increased from $10 in 2010 to $12.10 in 2006. Last year, the average price hit $13.37. Those averages are likely impacted by collectors' pieces. In 2015, the most expensive item sold on the site was Chung King Can Suck It by hardcore band Judge, which went for $5,958.36. The previous record was hit in 2011, when Mistifide’s Equidity Funk sold for $3,861.90.

Last year, 2.96 million users participated in a transaction on the site,'s up from 130,675 in 2005 and 3,273 in its second year.

As the site's popularity has grown, so too has its database. It currently lists some 6,464,362 titles -- if an album from a band was issued in 10 different countries in different languages, that would count as 10 titles.

According to Discogs' records, Fleetwood Mac's Rumours is the most-collected item this year; Jack White's Lazaretto was the most popular title in 2014. Prior to that, Daft Punk twice garnered the distinction of being the most collected item with Homework in 2010 and Random Access Memories in 2013; while Burial also earned that distinction twice too, with Street Halo in 2011 and Kindred in 2012.

To celebrate the occasion, Discogs has created a dynamic web page that goes through many of these stats -- take a look here.