Many book publishing companies around the world maintain a strict "no unsolicited submissions" policy and will only accept submissions via a literary agent. This shifts the burden of assessing and developing writers out of the publishing company and onto the literary agents. At these companies, unsolicited manuscripts are thrown out, or sometimes returned, if the author has provided pre-paid postage. Established authors are often represented by a literary agent to market their work to publishers and negotiate contracts. Literary agents take a percentage of author earnings (varying between 10 to 15 percent) to pay for their services.