Modern product development faces many challenges, including competitive forces from the global marketplace, highly constrained resources, and the need to keep pace with rapid technological change. A common response to the challenges is a formal process improvement program to ensure that product development processes are continuously improved in order to maximize both efficiency and effectiveness. At least six categories of such process improvement methodologies are in wide use today. Each category takes a unique perspective and includes specific methodologies that are applied to improve the product development processes. Contemporary improvement programs most often invoke two or more methodologies and are customized to the individual business culture and needs.