NEW YORK (Sept. 9)—Natural rubber prices skyrocketed in late August and early September, nearing the 50-cent-per-pound mark in both technically specified rubber and smoked sheets. "This is probably the highest it's been in three or four years," said Dennis J. Fenley, vice president of Patriot Trading Inc. in Danbury, Conn. While tight supplies, higher demand and a resurgent auto industry have all been given as reasons for higher prices, Fenley said there's also been a contest in Southeast Asia as to whom can drive prices up farthest. "A couple of traders in Singapore are bulling this market," he said. "This is a speculation-driven rise. There may be a little increase in demand, but not one that would make prices increase 25 percent in three weeks."