Pandora is to cap mobile listening hours at 40 per month for US users to address rising content costs relating to its listeners' use on the move.

Speaking in a blog post, Pandora founder Tim Westergren explains Pandora's per-track royalty rates "have increased more than 25% over the last three years, including 9% in 2013 alone and are scheduled to increase an additional 16% over the next two years."

He says the new measure “allows us to manage these escalating ...