LONDON — Edging downward from the October forecast, the world wheat carryover for 2012 was projected by the International Grains Council at 200 million tonnes, down 2 million from the month before and a modest 2% larger than the 196 million tonnes estimated for 2011. If realized, the world wheat carryover would extend a period of uncharacteristic stability, with 200 million tonnes in 2012 and 196 million in 2011 coming on the heels of 199 million in 2010. By contrast, the carryover was 172 million tonnes in 2009 and 132 million in 2008. Despite the tightening from a month earlier, U.S. wheat prices tumbled during the month, pressured by slumping U.S. corn price, the council said. “Heavy supplies of wheat amid strong export competition, including from new crop grain out of Argentina and Australia, mostly reduced f.o.b. values by between $20 and $30 over the past month, narrowing the gap with Black Sea quotations,” the I.G.C. said.