Rental income from supertankers plying the industry’s key route may stagnate this year after the worst December since at least 2001 as an expanding fleet cuts rates owners can charge for vessel charters. Returns from shipping Middle East oil to Asia averaged $18,417 a day in December, the worst performance for the final month of a year since at least 2001, according to data compiled by Bloomberg stretching back to that year. The route is the world’s busiest for very large crude carriers, or VLCCs.

The transportation capacity of the combined fleet of VLCCs and smaller aframax and suezmax tankers will expand 6.9 percent to 344.2 million deadweight tons in 2011, according to data from Clarkson Research Services Ltd., a unit of the world’s largest shipbroker. That would be more than four times the 1.6 percent climb in global oil demand to 88.8 million barrels a day next year predicted by the International Energy Agency.
“There are too many vessels coming out in too short a time,” Petter Narvestad, an analyst at Fondsfinans ASA in Oslo, said by phone. “We expect to see the tanker market struggle through 2011.”

Supply and demand today are “pretty much the same,” or “maybe a tad” more vessels are available for charter than before year-end holidays, Halvor Ellefsen, a shipbroker at SeaLeague A/S in Oslo, said by e-mail.