The Semiconductor Industry Assn. said the November book-to-bill ratio, a key barometer of industry health, was unchanged from the October rate of 1.07. It was the 12th straight positive monthly ratio recorded by the SIA. The ratio is a comparison of new computer chip orders from customers in the United States with shipments that fill old chip orders. November's 1.07 ratio means that for every $100 worth of shipments made during the period, the suppliers took $107 of orders. The October ratio was revised upward from 1.06. The SIA also revised the September ratio to 1.07 from 1.04.