EVOLUTIONARY TRENDS OF INDUSTRY VARIABLES

The paper offer's empirical evidence on the evolutionary trends of ind ustry variables. It investigates the time path of patents, product pri ce and quantity, and number of firms from the first introduction of a product to maturity of the market. The paper extends earlier work by G ort and Klepper by expanding the data on products through 1991, and au gmenting it with new products and new data sources. The reexamination of the aging patterns reveal the Gort and Klepper results to be robust . The time trends follow the expected patterns with remarkable consist ency and are strongly significant for most products. New evidence on p atenting activity reveal an eventual decline in technological activity over the later years of the product market life-cycle. (C) 1998 Elsev ier Science B.V.