1. Taken from: Cooper, R. G.Product Leadership: Creating and Launching Superior New Products. Reading, MA: Perseus Books, 1998, p. 189; and based on a study reported in: Cooper, R. G., S. J. Edgett and E. J. Kleinschmidt. “New product portfolio management: practices and performance.”Journal of Product Innovation Management, 16, 4, July 1999, pp. 333–351.