U.S. refiners are facing the prospects of weakening gasoline demand for the first time in five years, stoking fears that earnings this year may be even worse than the dismal performances seen in 2016. The sign of weakening U.S. gasoline demand comes as U.S. refiners are in the midst of reporting their worst year of earnings since the U.S. shale boom started in 2011. The oil boom turned to bust in 2014, and U.S. independent refiners reaped the profits as plunging pump prices and a growing economy helped fuel a surge in demand.