In most U.S. ports, docking fees, which are fees charged to ship owners for the right to dock, load and unload passengers or freight, are set by government agencies. In recent years, the demand for docking space at U.S. seaports has increased as the number of cruise ships and number of pleasure cruises have increased. Neither the prices charged to dock a ship nor the amount of docking space have changed as demand has increased. What kind of price control has been placed on docking space for ships?