A barrel is the standard unit of measurement for crude oil and petroleum products, equal to 42 US gallons or approximately 159 litres. Oil prices are typically quoted per barrel—when news reports say 'oil is trading at $80,' they mean $80 per barrel. The barrel became the standard measurement in the early American oil industry when crude was literally stored and transported in wooden barrels. In petroleum-producing provinces like Alberta and Saskatchewan, oil prices per barrel directly affect government royalty revenues, economic activity, and employment. Fluctuating barrel prices create boom-and-bust cycles in resource-dependent economies.