Specialized ratios are sometimes used in specific industries. For example, the so-called book-to-bill ratio is closely watched for semiconductor manufacturers. A ratio of .93 indicates that for every $100 worth of chips shipped over some period, only $93 worth of new orders were received. In January 2008, the semiconductor equipment industry's book-to-bill ratio was .89, compared to .85 during the month of December 2007. The book-to-bill ratio reached a recent low of .79 during September 2007. The three-month average of worldwide bookings in January 2008 was $1.12 billion, a decrease of 3 percent from December 2007, while the three-month average of billings was $1.27 billion, a 7 percent decrease from December 2007. What is this ratio intended to measure? Why do you think it is so closely followed?