Tumblr founder David Karp has revealed new numbers that shed some light on the blogging service's growth and business model. In comments reported by TechCrunch, Karp says that the site now garners 20 billion pageviews a month, representing a big jump over the past year or so; Tumblr reported figures of 13 billion last September.

Such high volume would no doubt provide a dream platform for advertisers — except Tumblr isn't selling. The service keeps its blogs free from banner ads, instead electing to rent out a small space for sponsored content on the main dashboard. This means that only around 120 million page views a day end up being monetized, equating to roughly 18 percent of the site's traffic.

"There are no brand pages or promoted posts. The one difference advertisers have is that they're able to write a check to elevate their stuff in this ecosystem."

Karp has said in the past that Tumblr could be "wildly profitable" by going down the path of traditional internet advertising, but doesn't want to compromise the platform's "mission of enabling creators around the world." While Tumblr has subsisted to date on over $125 million in venture capital, it remains unclear if its current business model will bring it into the black.