Saturday effects in tanker oil spills

This paper documents a “Saturday effect” in the timing of tanker oil spills—certain types of spills happen much more frequently on this day than one would expect if the spills were uniformly distributed. The phenomenon is restricted to Europe and North America, and is associated with “vessel guidance” accidents—groundings, collisions, and rammings. Eliminating the Saturday effect would reduce tanker oil spills by around 163,000 gallons per year. Several policy responses are considered, including a Saturday harbor tax. A lower bound for an efficient tax is estimated to be $780 for a 20 million gal cargo.