A Book-To-Bill Ratio is the ratio of orders received to units shipped and invoiced during a given time period, usually a month or quarter. It is a popular statistic in the technology business, particularly in the semiconductor equipment industry. This ratio is frequently monitored by investors and analysts as an indicator of the performance and prognosis for individual firms as well as the technology industry as a whole. A ratio greater than one indicates that more orders were received than filled, suggesting high demand, whilst a ratio less than one indicates lower demand.The book-to-bill ration can be used to measure both supply and demand within an industry. When there is excess demand (a book-to-bill ration > 1), suppliers are able to increase prices since there are more buyers competing for limited goods; however, when there is excess supply (book-to bill ration < 1), prices tend to drop because sellers have to compete with each other for buyers.