Last week, Spotify turned five years old, and to celebrate, the company released a batch of impressive data. But buried within the fun facts is a tidbit that's just as depressing as it is surprising: 20-percent of Spotify tracks have never been streamed.

Of course, Spotify cast a positive light on the information: 80-percent of the songs in the catalog have actually been streamed at least once. Presented this way, it's quite a shock that Spotify's 24 million monthly users have meandered their way out to that much music. For example, you'd never think that somebody actually listens to obscurities like Squab Teen, but lo, they've got three followers on Spotify (this blogger included).

Music services love (LOVE!) to tout the size of their catalogs. Spotify, like Rdio, Xbox Music, and iTunes Radio all brag about their catalogs that all contain more than 20 million songs. But it's easy to forget that a huge selection of songs that nobody wants to listen to doesn't really mean anything. Consider that Pandora defends its relatively meager 1 million song catalog by saying it's not that quantity of songs that matters but rather the quality of the selection and of the service that helps people discover the music. Spotify's 80-percent metric suggests that, yes, users are making it out to the nether regions of Spotify's catalog and by proxy, that Spotify's doing a decent job of getting them out there.

Still, those 4 million unstreamed jams must be lonely. Can you spare a stream for a starving song? [Spotify via Buzzfeed]