US Treasury Secretary Paulson may find his call for China to continue allowing the yuan to appreciate versus the dollar falling on deaf ears. Indeed in recent days the yuan has seen a sudden drop in value, which some see as a possible signal of a policy shift to help prop up Chinese exports at a time of spluttering economic growth. The yuan fell by its maximum daily trading limit for a second consecutive day Tuesday, the central parity rate rising to 6.8527 from 6.8505 Monday and 6.8349 Friday.