Market share is not always a consideration, because not all radio stations are commercial. Public radio is funded by government and private donors. Since most public broadcasting operations don't have to make a profit, no commercials are necessary. (In fact, because most public broadcasting stations operate under noncommercial licenses from their country's broadcasting regulator, they may not be allowed to sell advertising at all.) Underwriting spots, which mention the name of a sponsor and some information but cannot include “calls to action” attempting to convince the listener to patronize the sponsor, may be allowed.