ByJohn S. McClenahen Although a majority of senior U.S. manufacturing executives are optimistic about the American economy's prospects during the next 12 months, they are slightly less so than are executives from a cross-section of industries, according to a new quarterly survey from PricewaterhouseCoopers. Eighty senior executives in large manufacturing multinationals and 97 senior executives in a cross-section of other industries were interviewed during this year's third calendar quarter. Some 70% of the manufacturing executives were optimistic about the short-term economic outlook, compared with 73% of the executives from a cross-section of industries, including manufacturing. Neither group is as optimistic about the short-term outlook for the world economy, however. Only 46% of the executives in each category are upbeat on the next 12 months.